Add frozen

src/frozen/LICENSE

@@ -0,0 +1,16 @@
+Copyright (c) 2004-2013 Sergey Lyubka <valenok@gmail.com>
+Copyright (c) 2013 Cesanta Software Limited
+All rights reserved
+
+This code is dual-licensed: you can redistribute it and/or modify
+it under the terms of the GNU General Public License version 2 as
+published by the Free Software Foundation. For the terms of this
+license, see <http://www.gnu.org/licenses/>.
+
+You are free to use this code under the terms of the GNU General
+Public License, but WITHOUT ANY WARRANTY; without even the implied
+warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+See the GNU General Public License for more details.
+
+Alternatively, you can license this code under a commercial
+license, as set out in <http://cesanta.com/>.

src/frozen/frozen.c

@@ -0,0 +1,994 @@
+/*
+ * Copyright (c) 2004-2013 Sergey Lyubka <valenok@gmail.com>
+ * Copyright (c) 2013 Cesanta Software Limited
+ * All rights reserved
+ *
+ * This library is dual-licensed: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation. For the terms of this
+ * license, see <http: *www.gnu.org/licenses/>.
+ *
+ * You are free to use this library under the terms of the GNU General
+ * Public License, but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * Alternatively, you can license this library under a commercial
+ * license, as set out in <http://cesanta.com/products.html>.
+ */
+
+#define _CRT_SECURE_NO_WARNINGS /* Disable deprecation warning in VS2005+ */
+
+#include "frozen.h"
+#include <ctype.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#if !defined(WEAK)
+#if (defined(__GNUC__) || defined(__TI_COMPILER_VERSION__)) && !defined(_WIN32)
+#define WEAK __attribute__((weak))
+#else
+#define WEAK
+#endif
+#endif
+
+#ifdef _WIN32
+#define snprintf cs_win_snprintf
+#define vsnprintf cs_win_vsnprintf
+int cs_win_snprintf(char *str, size_t size, const char *format, ...);
+int cs_win_vsnprintf(char *str, size_t size, const char *format, va_list ap);
+#if _MSC_VER >= 1700
+#include <stdint.h>
+#else
+typedef _int64 int64_t;
+typedef unsigned _int64 uint64_t;
+#endif
+#define PRId64 "I64d"
+#define PRIu64 "I64u"
+#if !defined(SIZE_T_FMT)
+#if _MSC_VER >= 1310
+#define SIZE_T_FMT "Iu"
+#else
+#define SIZE_T_FMT "u"
+#endif
+#endif
+#else /* _WIN32 */
+/* <inttypes.h> wants this for C++ */
+#ifndef __STDC_FORMAT_MACROS
+#define __STDC_FORMAT_MACROS
+#endif
+#include <inttypes.h>
+#if !defined(SIZE_T_FMT)
+#define SIZE_T_FMT "zu"
+#endif
+#endif /* _WIN32 */
+
+#define INT64_FMT PRId64
+#define UINT64_FMT PRIu64
+
+#ifndef va_copy
+#define va_copy(x, y) x = y
+#endif
+
+#ifndef JSON_MAX_PATH_LEN
+#define JSON_MAX_PATH_LEN 60
+#endif
+
+struct frozen {
+  const char *end;
+  const char *cur;
+
+  const char *cur_name;
+  size_t cur_name_len;
+
+  /* For callback API */
+  char path[JSON_MAX_PATH_LEN];
+  int path_len;
+  void *callback_data;
+  json_walk_callback_t callback;
+};
+
+struct fstate {
+  const char *ptr;
+  int path_len;
+};
+
+#define SET_STATE(fr, ptr, str, len)              \
+  struct fstate fstate = {(ptr), (fr)->path_len}; \
+  append_to_path((fr), (str), (len));
+
+#define CALL_BACK(fr, tok, value, len)                                        \
+  do {                                                                        \
+    if ((fr)->callback &&                                                     \
+        ((fr)->path_len == 0 || (fr)->path[(fr)->path_len - 1] != '.')) {     \
+      struct json_token t = {(value), (len), (tok)};                          \
+                                                                              \
+      /* Call the callback with the given value and current name */           \
+      (fr)->callback((fr)->callback_data, (fr)->cur_name, (fr)->cur_name_len, \
+                     (fr)->path, &t);                                         \
+                                                                              \
+      /* Reset the name */                                                    \
+      (fr)->cur_name = NULL;                                                  \
+      (fr)->cur_name_len = 0;                                                 \
+    }                                                                         \
+  } while (0)
+
+static int append_to_path(struct frozen *f, const char *str, int size) {
+  int n = f->path_len;
+  f->path_len +=
+      snprintf(f->path + f->path_len, sizeof(f->path) - (f->path_len + 1),
+               "%.*s", size, str);
+
+  return n;
+}
+
+static void truncate_path(struct frozen *f, int len) {
+  f->path_len = len;
+  f->path[len] = '\0';
+}
+
+static int parse_object(struct frozen *f);
+static int parse_value(struct frozen *f);
+
+#define EXPECT(cond, err_code)      \
+  do {                              \
+    if (!(cond)) return (err_code); \
+  } while (0)
+
+#define TRY(expr)          \
+  do {                     \
+    int _n = expr;         \
+    if (_n < 0) return _n; \
+  } while (0)
+
+#define END_OF_STRING (-1)
+
+static int left(const struct frozen *f) {
+  return f->end - f->cur;
+}
+
+static int is_space(int ch) {
+  return ch == ' ' || ch == '\t' || ch == '\r' || ch == '\n';
+}
+
+static void skip_whitespaces(struct frozen *f) {
+  while (f->cur < f->end && is_space(*f->cur)) f->cur++;
+}
+
+static int cur(struct frozen *f) {
+  skip_whitespaces(f);
+  return f->cur >= f->end ? END_OF_STRING : *(unsigned char *) f->cur;
+}
+
+static int test_and_skip(struct frozen *f, int expected) {
+  int ch = cur(f);
+  if (ch == expected) {
+    f->cur++;
+    return 0;
+  }
+  return ch == END_OF_STRING ? JSON_STRING_INCOMPLETE : JSON_STRING_INVALID;
+}
+
+static int is_alpha(int ch) {
+  return (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z');
+}
+
+static int is_digit(int ch) {
+  return ch >= '0' && ch <= '9';
+}
+
+static int is_hex_digit(int ch) {
+  return is_digit(ch) || (ch >= 'a' && ch <= 'f') || (ch >= 'A' && ch <= 'F');
+}
+
+static int get_escape_len(const char *s, int len) {
+  switch (*s) {
+    case 'u':
+      return len < 6 ? JSON_STRING_INCOMPLETE
+                     : is_hex_digit(s[1]) && is_hex_digit(s[2]) &&
+                               is_hex_digit(s[3]) && is_hex_digit(s[4])
+                           ? 5
+                           : JSON_STRING_INVALID;
+    case '"':
+    case '\\':
+    case '/':
+    case 'b':
+    case 'f':
+    case 'n':
+    case 'r':
+    case 't':
+      return len < 2 ? JSON_STRING_INCOMPLETE : 1;
+    default:
+      return JSON_STRING_INVALID;
+  }
+}
+
+/* identifier = letter { letter | digit | '_' } */
+static int parse_identifier(struct frozen *f) {
+  EXPECT(is_alpha(cur(f)), JSON_STRING_INVALID);
+  {
+    SET_STATE(f, f->cur, "", 0);
+    while (f->cur < f->end &&
+           (*f->cur == '_' || is_alpha(*f->cur) || is_digit(*f->cur))) {
+      f->cur++;
+    }
+    truncate_path(f, fstate.path_len);
+    CALL_BACK(f, JSON_TYPE_STRING, fstate.ptr, f->cur - fstate.ptr);
+  }
+  return 0;
+}
+
+static int get_utf8_char_len(unsigned char ch) {
+  if ((ch & 0x80) == 0) return 1;
+  switch (ch & 0xf0) {
+    case 0xf0:
+      return 4;
+    case 0xe0:
+      return 3;
+    default:
+      return 2;
+  }
+}
+
+/* string = '"' { quoted_printable_chars } '"' */
+static int parse_string(struct frozen *f) {
+  int n, ch = 0, len = 0;
+  TRY(test_and_skip(f, '"'));
+  {
+    SET_STATE(f, f->cur, "", 0);
+    for (; f->cur < f->end; f->cur += len) {
+      ch = *(unsigned char *) f->cur;
+      len = get_utf8_char_len((unsigned char) ch);
+      EXPECT(ch >= 32 && len > 0, JSON_STRING_INVALID); /* No control chars */
+      EXPECT(len < left(f), JSON_STRING_INCOMPLETE);
+      if (ch == '\\') {
+        EXPECT((n = get_escape_len(f->cur + 1, left(f))) > 0, n);
+        len += n;
+      } else if (ch == '"') {
+        truncate_path(f, fstate.path_len);
+        CALL_BACK(f, JSON_TYPE_STRING, fstate.ptr, f->cur - fstate.ptr);
+        f->cur++;
+        break;
+      };
+    }
+  }
+  return ch == '"' ? 0 : JSON_STRING_INCOMPLETE;
+}
+
+/* number = [ '-' ] digit+ [ '.' digit+ ] [ ['e'|'E'] ['+'|'-'] digit+ ] */
+static int parse_number(struct frozen *f) {
+  int ch = cur(f);
+  SET_STATE(f, f->cur, "", 0);
+  if (ch == '-') f->cur++;
+  EXPECT(f->cur < f->end, JSON_STRING_INCOMPLETE);
+  EXPECT(is_digit(f->cur[0]), JSON_STRING_INVALID);
+  while (f->cur < f->end && is_digit(f->cur[0])) f->cur++;
+  if (f->cur < f->end && f->cur[0] == '.') {
+    f->cur++;
+    EXPECT(f->cur < f->end, JSON_STRING_INCOMPLETE);
+    EXPECT(is_digit(f->cur[0]), JSON_STRING_INVALID);
+    while (f->cur < f->end && is_digit(f->cur[0])) f->cur++;
+  }
+  if (f->cur < f->end && (f->cur[0] == 'e' || f->cur[0] == 'E')) {
+    f->cur++;
+    EXPECT(f->cur < f->end, JSON_STRING_INCOMPLETE);
+    if ((f->cur[0] == '+' || f->cur[0] == '-')) f->cur++;
+    EXPECT(f->cur < f->end, JSON_STRING_INCOMPLETE);
+    EXPECT(is_digit(f->cur[0]), JSON_STRING_INVALID);
+    while (f->cur < f->end && is_digit(f->cur[0])) f->cur++;
+  }
+  truncate_path(f, fstate.path_len);
+  CALL_BACK(f, JSON_TYPE_NUMBER, fstate.ptr, f->cur - fstate.ptr);
+  return 0;
+}
+
+/* array = '[' [ value { ',' value } ] ']' */
+static int parse_array(struct frozen *f) {
+  int i = 0, current_path_len;
+  char buf[20];
+  TRY(test_and_skip(f, '['));
+  {
+    CALL_BACK(f, JSON_TYPE_ARRAY_START, NULL, 0);
+    {
+      SET_STATE(f, f->cur - 1, "", 0);
+      while (cur(f) != ']') {
+        snprintf(buf, sizeof(buf), "[%d]", i);
+        i++;
+        current_path_len = append_to_path(f, buf, strlen(buf));
+        f->cur_name =
+            f->path + strlen(f->path) - strlen(buf) + 1 /*opening brace*/;
+        f->cur_name_len = strlen(buf) - 2 /*braces*/;
+        TRY(parse_value(f));
+        truncate_path(f, current_path_len);
+        if (cur(f) == ',') f->cur++;
+      }
+      TRY(test_and_skip(f, ']'));
+      truncate_path(f, fstate.path_len);
+      CALL_BACK(f, JSON_TYPE_ARRAY_END, fstate.ptr, f->cur - fstate.ptr);
+    }
+  }
+  return 0;
+}
+
+static int expect(struct frozen *f, const char *s, int len,
+                  enum json_token_type tok_type) {
+  int i, n = left(f);
+  SET_STATE(f, f->cur, "", 0);
+  for (i = 0; i < len; i++) {
+    if (i >= n) return JSON_STRING_INCOMPLETE;
+    if (f->cur[i] != s[i]) return JSON_STRING_INVALID;
+  }
+  f->cur += len;
+  truncate_path(f, fstate.path_len);
+
+  CALL_BACK(f, tok_type, fstate.ptr, f->cur - fstate.ptr);
+
+  return 0;
+}
+
+/* value = 'null' | 'true' | 'false' | number | string | array | object */
+static int parse_value(struct frozen *f) {
+  int ch = cur(f);
+
+  switch (ch) {
+    case '"':
+      TRY(parse_string(f));
+      break;
+    case '{':
+      TRY(parse_object(f));
+      break;
+    case '[':
+      TRY(parse_array(f));
+      break;
+    case 'n':
+      TRY(expect(f, "null", 4, JSON_TYPE_NULL));
+      break;
+    case 't':
+      TRY(expect(f, "true", 4, JSON_TYPE_TRUE));
+      break;
+    case 'f':
+      TRY(expect(f, "false", 5, JSON_TYPE_FALSE));
+      break;
+    case '-':
+    case '0':
+    case '1':
+    case '2':
+    case '3':
+    case '4':
+    case '5':
+    case '6':
+    case '7':
+    case '8':
+    case '9':
+      TRY(parse_number(f));
+      break;
+    default:
+      return ch == END_OF_STRING ? JSON_STRING_INCOMPLETE : JSON_STRING_INVALID;
+  }
+
+  return 0;
+}
+
+/* key = identifier | string */
+static int parse_key(struct frozen *f) {
+  int ch = cur(f);
+#if 0
+  printf("%s [%.*s]\n", __func__, (int) (f->end - f->cur), f->cur);
+#endif
+  if (is_alpha(ch)) {
+    TRY(parse_identifier(f));
+  } else if (ch == '"') {
+    TRY(parse_string(f));
+  } else {
+    return ch == END_OF_STRING ? JSON_STRING_INCOMPLETE : JSON_STRING_INVALID;
+  }
+  return 0;
+}
+
+/* pair = key ':' value */
+static int parse_pair(struct frozen *f) {
+  int current_path_len;
+  const char *tok;
+  skip_whitespaces(f);
+  tok = f->cur;
+  TRY(parse_key(f));
+  {
+    f->cur_name = *tok == '"' ? tok + 1 : tok;
+    f->cur_name_len = *tok == '"' ? f->cur - tok - 2 : f->cur - tok;
+    current_path_len = append_to_path(f, f->cur_name, f->cur_name_len);
+  }
+  TRY(test_and_skip(f, ':'));
+  TRY(parse_value(f));
+  truncate_path(f, current_path_len);
+  return 0;
+}
+
+/* object = '{' pair { ',' pair } '}' */
+static int parse_object(struct frozen *f) {
+  TRY(test_and_skip(f, '{'));
+  {
+    CALL_BACK(f, JSON_TYPE_OBJECT_START, NULL, 0);
+    {
+      SET_STATE(f, f->cur - 1, ".", 1);
+      while (cur(f) != '}') {
+        TRY(parse_pair(f));
+        if (cur(f) == ',') f->cur++;
+      }
+      TRY(test_and_skip(f, '}'));
+      truncate_path(f, fstate.path_len);
+      CALL_BACK(f, JSON_TYPE_OBJECT_END, fstate.ptr, f->cur - fstate.ptr);
+    }
+  }
+  return 0;
+}
+
+static int doit(struct frozen *f) {
+  if (f->cur == 0 || f->end < f->cur) return JSON_STRING_INVALID;
+  if (f->end == f->cur) return JSON_STRING_INCOMPLETE;
+  return parse_value(f);
+}
+
+static int json_encode_string(struct json_out *out, const char *p, size_t len) {
+  size_t i, cl, n = 0;
+  const char *hex_digits = "0123456789abcdef";
+  const char *specials = "btnvfr";
+
+  for (i = 0; i < len; i++) {
+    unsigned char ch = ((unsigned char *) p)[i];
+    if (ch == '"' || ch == '\\') {
+      n += out->printer(out, "\\", 1);
+      n += out->printer(out, p + i, 1);
+    } else if (ch >= '\b' && ch <= '\r') {
+      n += out->printer(out, "\\", 1);
+      n += out->printer(out, &specials[ch - '\b'], 1);
+    } else if (isprint(ch)) {
+      n += out->printer(out, p + i, 1);
+    } else if ((cl = get_utf8_char_len(ch)) == 1) {
+      n += out->printer(out, "\\u00", 4);
+      n += out->printer(out, &hex_digits[(ch >> 4) % 0xf], 1);
+      n += out->printer(out, &hex_digits[ch % 0xf], 1);
+    } else {
+      n += out->printer(out, p + i, cl);
+      i += cl - 1;
+    }
+  }
+
+  return n;
+}
+
+int json_printer_buf(struct json_out *out, const char *buf, size_t len) WEAK;
+int json_printer_buf(struct json_out *out, const char *buf, size_t len) {
+  size_t avail = out->u.buf.size - out->u.buf.len;
+  size_t n = len < avail ? len : avail;
+  memcpy(out->u.buf.buf + out->u.buf.len, buf, n);
+  out->u.buf.len += n;
+  if (out->u.buf.size > 0) {
+    size_t idx = out->u.buf.len;
+    if (idx >= out->u.buf.size) idx = out->u.buf.size - 1;
+    out->u.buf.buf[idx] = '\0';
+  }
+  return len;
+}
+
+int json_printer_file(struct json_out *out, const char *buf, size_t len) WEAK;
+int json_printer_file(struct json_out *out, const char *buf, size_t len) {
+  return fwrite(buf, 1, len, out->u.fp);
+}
+
+static int b64idx(int c) {
+  if (c < 26) {
+    return c + 'A';
+  } else if (c < 52) {
+    return c - 26 + 'a';
+  } else if (c < 62) {
+    return c - 52 + '0';
+  } else {
+    return c == 62 ? '+' : '/';
+  }
+}
+
+static int b64rev(int c) {
+  if (c >= 'A' && c <= 'Z') {
+    return c - 'A';
+  } else if (c >= 'a' && c <= 'z') {
+    return c + 26 - 'a';
+  } else if (c >= '0' && c <= '9') {
+    return c + 52 - '0';
+  } else if (c == '+') {
+    return 62;
+  } else if (c == '/') {
+    return 63;
+  } else {
+    return 64;
+  }
+}
+
+static uint8_t hexdec(const char *s) {
+#define HEXTOI(x) (x >= '0' && x <= '9' ? x - '0' : x - 'W')
+  int a = tolower(*(const unsigned char *) s);
+  int b = tolower(*(const unsigned char *) (s + 1));
+  return (HEXTOI(a) << 4) | HEXTOI(b);
+}
+
+static int b64enc(struct json_out *out, const unsigned char *p, int n) {
+  char buf[4];
+  int i, len = 0;
+  for (i = 0; i < n; i += 3) {
+    int a = p[i], b = i + 1 < n ? p[i + 1] : 0, c = i + 2 < n ? p[i + 2] : 0;
+    buf[0] = b64idx(a >> 2);
+    buf[1] = b64idx((a & 3) << 4 | (b >> 4));
+    buf[2] = b64idx((b & 15) << 2 | (c >> 6));
+    buf[3] = b64idx(c & 63);
+    if (i + 1 >= n) buf[2] = '=';
+    if (i + 2 >= n) buf[3] = '=';
+    len += out->printer(out, buf, sizeof(buf));
+  }
+  return len;
+}
+
+static int b64dec(const char *src, int n, char *dst) {
+  const char *end = src + n;
+  int len = 0;
+  while (src + 3 < end) {
+    int a = b64rev(src[0]), b = b64rev(src[1]), c = b64rev(src[2]),
+        d = b64rev(src[3]);
+    dst[len++] = (a << 2) | (b >> 4);
+    if (src[2] != '=') {
+      dst[len++] = (b << 4) | (c >> 2);
+      if (src[3] != '=') {
+        dst[len++] = (c << 6) | d;
+      }
+    }
+    src += 4;
+  }
+  return len;
+}
+
+int json_vprintf(struct json_out *out, const char *fmt, va_list xap) WEAK;
+int json_vprintf(struct json_out *out, const char *fmt, va_list xap) {
+  int len = 0;
+  const char *quote = "\"", *null = "null";
+  va_list ap;
+  va_copy(ap, xap);
+
+  while (*fmt != '\0') {
+    if (strchr(":, \r\n\t[]{}\"", *fmt) != NULL) {
+      len += out->printer(out, fmt, 1);
+      fmt++;
+    } else if (fmt[0] == '%') {
+      char buf[21];
+      size_t skip = 2;
+
+      if (fmt[1] == 'l' && fmt[2] == 'l' && (fmt[3] == 'd' || fmt[3] == 'u')) {
+        int64_t val = va_arg(ap, int64_t);
+        const char *fmt2 = fmt[3] == 'u' ? "%" UINT64_FMT : "%" INT64_FMT;
+        snprintf(buf, sizeof(buf), fmt2, val);
+        len += out->printer(out, buf, strlen(buf));
+        skip += 2;
+      } else if (fmt[1] == 'z' && fmt[2] == 'u') {
+        size_t val = va_arg(ap, size_t);
+        snprintf(buf, sizeof(buf), "%" SIZE_T_FMT, val);
+        len += out->printer(out, buf, strlen(buf));
+        skip += 1;
+      } else if (fmt[1] == 'M') {
+        json_printf_callback_t f = va_arg(ap, json_printf_callback_t);
+        len += f(out, &ap);
+      } else if (fmt[1] == 'B') {
+        int val = va_arg(ap, int);
+        const char *str = val ? "true" : "false";
+        len += out->printer(out, str, strlen(str));
+      } else if (fmt[1] == 'H') {
+        const char *hex = "0123456789abcdef";
+        int i, n = va_arg(ap, int);
+        const unsigned char *p = va_arg(ap, const unsigned char *);
+        len += out->printer(out, quote, 1);
+        for (i = 0; i < n; i++) {
+          len += out->printer(out, &hex[(p[i] >> 4) & 0xf], 1);
+          len += out->printer(out, &hex[p[i] & 0xf], 1);
+        }
+        len += out->printer(out, quote, 1);
+      } else if (fmt[1] == 'V') {
+        const unsigned char *p = va_arg(ap, const unsigned char *);
+        int n = va_arg(ap, int);
+        len += out->printer(out, quote, 1);
+        len += b64enc(out, p, n);
+        len += out->printer(out, quote, 1);
+      } else if (fmt[1] == 'Q' ||
+                 (fmt[1] == '.' && fmt[2] == '*' && fmt[3] == 'Q')) {
+        size_t l = 0;
+        const char *p;
+
+        if (fmt[1] == '.') {
+          l = (size_t) va_arg(ap, int);
+          skip += 2;
+        }
+        p = va_arg(ap, char *);
+
+        if (p == NULL) {
+          len += out->printer(out, null, 4);
+        } else {
+          if (fmt[1] == 'Q') {
+            l = strlen(p);
+          }
+          len += out->printer(out, quote, 1);
+          len += json_encode_string(out, p, l);
+          len += out->printer(out, quote, 1);
+        }
+      } else {
+        /*
+         * we delegate printing to the system printf.
+         * The goal here is to delegate all modifiers parsing to the system
+         * printf, as you can see below we still have to parse the format
+         * types.
+         *
+         * Currently, %s with strings longer than 20 chars will require
+         * double-buffering (an auxiliary buffer will be allocated from heap).
+         * TODO(dfrank): reimplement %s and %.*s in order to avoid that.
+         */
+
+        const char *end_of_format_specifier = "sdfFgGlhuI.*-0123456789";
+        size_t n = strspn(fmt + 1, end_of_format_specifier);
+        char *pbuf = buf;
+        size_t need_len;
+        char fmt2[20];
+        va_list sub_ap;
+        strncpy(fmt2, fmt, n + 1 > sizeof(fmt2) ? sizeof(fmt2) : n + 1);
+        fmt2[n + 1] = '\0';
+
+        va_copy(sub_ap, ap);
+        need_len =
+            vsnprintf(buf, sizeof(buf), fmt2, sub_ap) + 1 /* null-term */;
+        /*
+         * TODO(lsm): Fix windows & eCos code path here. Their vsnprintf
+         * implementation returns -1 on overflow rather needed size.
+         */
+        if (need_len > sizeof(buf)) {
+          /*
+           * resulting string doesn't fit into a stack-allocated buffer `buf`,
+           * so we need to allocate a new buffer from heap and use it
+           */
+          pbuf = (char *) malloc(need_len);
+          va_copy(sub_ap, ap);
+          vsnprintf(pbuf, need_len, fmt2, sub_ap);
+        }
+
+        /*
+         * however we need to parse the type ourselves in order to advance
+         * the va_list by the correct amount; there is no portable way to
+         * inherit the advancement made by vprintf.
+         * 32-bit (linux or windows) passes va_list by value.
+         */
+        if ((n + 1 == strlen("%" PRId64) && strcmp(fmt2, "%" PRId64) == 0) ||
+            (n + 1 == strlen("%" PRIu64) && strcmp(fmt2, "%" PRIu64) == 0)) {
+          (void) va_arg(ap, int64_t);
+          skip += strlen(PRIu64) - 1;
+        } else if (strcmp(fmt2, "%.*s") == 0) {
+          (void) va_arg(ap, int);
+          (void) va_arg(ap, char *);
+        } else {
+          switch (fmt2[n]) {
+            case 'u':
+            case 'd':
+              (void) va_arg(ap, int);
+              break;
+            case 'g':
+            case 'f':
+              (void) va_arg(ap, double);
+              break;
+            case 'p':
+              (void) va_arg(ap, void *);
+              break;
+            default:
+              /* many types are promoted to int */
+              (void) va_arg(ap, int);
+          }
+        }
+
+        len += out->printer(out, pbuf, strlen(pbuf));
+        skip = n + 1;
+
+        /* If buffer was allocated from heap, free it */
+        if (pbuf != buf) {
+          free(pbuf);
+          pbuf = NULL;
+        }
+      }
+      fmt += skip;
+    } else if (*fmt == '_' || is_alpha(*fmt)) {
+      len += out->printer(out, quote, 1);
+      while (*fmt == '_' || is_alpha(*fmt) || is_digit(*fmt)) {
+        len += out->printer(out, fmt, 1);
+        fmt++;
+      }
+      len += out->printer(out, quote, 1);
+    } else {
+      fmt++;
+    }
+  }
+  va_end(ap);
+
+  return len;
+}
+
+int json_printf(struct json_out *out, const char *fmt, ...) WEAK;
+int json_printf(struct json_out *out, const char *fmt, ...) {
+  int n;
+  va_list ap;
+  va_start(ap, fmt);
+  n = json_vprintf(out, fmt, ap);
+  va_end(ap);
+  return n;
+}
+
+int json_printf_array(struct json_out *out, va_list *ap) WEAK;
+int json_printf_array(struct json_out *out, va_list *ap) {
+  int len = 0;
+  char *arr = va_arg(*ap, char *);
+  size_t i, arr_size = va_arg(*ap, size_t);
+  size_t elem_size = va_arg(*ap, size_t);
+  const char *fmt = va_arg(*ap, char *);
+  len += json_printf(out, "[", 1);
+  for (i = 0; arr != NULL && i < arr_size / elem_size; i++) {
+    union {
+      int64_t i;
+      double d;
+    } val;
+    memcpy(&val, arr + i * elem_size,
+           elem_size > sizeof(val) ? sizeof(val) : elem_size);
+    if (i > 0) len += json_printf(out, ", ");
+    if (strchr(fmt, 'f') != NULL) {
+      len += json_printf(out, fmt, val.d);
+    } else {
+      len += json_printf(out, fmt, val.i);
+    }
+  }
+  len += json_printf(out, "]", 1);
+  return len;
+}
+
+#ifdef _WIN32
+int cs_win_vsnprintf(char *str, size_t size, const char *format, va_list ap) WEAK;
+int cs_win_vsnprintf(char *str, size_t size, const char *format, va_list ap) {
+  int res = _vsnprintf(str, size, format, ap);
+  va_end(ap);
+  if (res >= size) {
+    str[size - 1] = '\0';
+  }
+  return res;
+}
+
+int cs_win_snprintf(char *str, size_t size, const char *format, ...) WEAK;
+int cs_win_snprintf(char *str, size_t size, const char *format, ...) {
+  int res;
+  va_list ap;
+  va_start(ap, format);
+  res = vsnprintf(str, size, format, ap);
+  va_end(ap);
+  return res;
+}
+#endif /* _WIN32 */
+
+int json_walk(const char *json_string, int json_string_length,
+              json_walk_callback_t callback, void *callback_data) WEAK;
+int json_walk(const char *json_string, int json_string_length,
+              json_walk_callback_t callback, void *callback_data) {
+  struct frozen frozen;
+
+  memset(&frozen, 0, sizeof(frozen));
+  frozen.end = json_string + json_string_length;
+  frozen.cur = json_string;
+  frozen.callback_data = callback_data;
+  frozen.callback = callback;
+
+  TRY(doit(&frozen));
+
+  return frozen.cur - json_string;
+}
+
+struct scan_array_info {
+  char path[JSON_MAX_PATH_LEN];
+  struct json_token *token;
+};
+
+static void json_scanf_array_elem_cb(void *callback_data, const char *name,
+                                     size_t name_len, const char *path,
+                                     const struct json_token *token) {
+  struct scan_array_info *info = (struct scan_array_info *) callback_data;
+
+  (void) name;
+  (void) name_len;
+
+  if (strcmp(path, info->path) == 0) {
+    *info->token = *token;
+  }
+}
+
+int json_scanf_array_elem(const char *s, int len, const char *path, int idx,
+                          struct json_token *token) WEAK;
+int json_scanf_array_elem(const char *s, int len, const char *path, int idx,
+                          struct json_token *token) {
+  struct scan_array_info info;
+  info.token = token;
+  memset(token, 0, sizeof(*token));
+  snprintf(info.path, sizeof(info.path), "%s[%d]", path, idx);
+  json_walk(s, len, json_scanf_array_elem_cb, &info);
+  return token->len;
+}
+
+struct json_scanf_info {
+  int num_conversions;
+  char *path;
+  const char *fmt;
+  void *target;
+  void *user_data;
+  int type;
+};
+
+int json_unescape(const char *src, int slen, char *dst, int dlen) WEAK;
+int json_unescape(const char *src, int slen, char *dst, int dlen) {
+  char *send = (char *) src + slen, *dend = dst + dlen, *orig_dst = dst, *p;
+  const char *esc1 = "\"\\/bfnrt", *esc2 = "\"\\/\b\f\n\r\t";
+
+  while (src < send) {
+    if (*src == '\\') {
+      if (++src >= send) return JSON_STRING_INCOMPLETE;
+      if (*src == 'u') {
+        /* TODO(lsm): \uXXXX escapes drag utf8 lib... Do it at some stage */
+        return JSON_STRING_INVALID;
+      } else if ((p = (char *) strchr(esc1, *src)) != NULL) {
+        if (dst < dend) *dst = esc2[p - esc1];
+      } else {
+        return JSON_STRING_INVALID;
+      }
+    } else {
+      if (dst < dend) *dst = *src;
+    }
+    dst++;
+    src++;
+  }
+
+  return dst - orig_dst;
+}
+
+static void json_scanf_cb(void *callback_data, const char *name,
+                          size_t name_len, const char *path,
+                          const struct json_token *token) {
+  struct json_scanf_info *info = (struct json_scanf_info *) callback_data;
+
+  (void) name;
+  (void) name_len;
+
+  if (strcmp(path, info->path) != 0) {
+    /* It's not the path we're looking for, so, just ignore this callback */
+    return;
+  }
+
+  if (token->ptr == NULL) {
+    /*
+     * We're not interested here in the events for which we have no value;
+     * namely, JSON_TYPE_OBJECT_START and JSON_TYPE_ARRAY_START
+     */
+    return;
+  }
+
+  switch (info->type) {
+    case 'B':
+      info->num_conversions++;
+      *(int *) info->target = (token->type == JSON_TYPE_TRUE ? 1 : 0);
+      break;
+    case 'M': {
+      union {
+        void *p;
+        json_scanner_t f;
+      } u = {info->target};
+      info->num_conversions++;
+      u.f(token->ptr, token->len, info->user_data);
+      break;
+    }
+    case 'Q': {
+      char **dst = (char **) info->target;
+      int unescaped_len = json_unescape(token->ptr, token->len, NULL, 0);
+      if (unescaped_len >= 0 &&
+          (*dst = (char *) malloc(unescaped_len + 1)) != NULL) {
+        info->num_conversions++;
+        json_unescape(token->ptr, token->len, *dst, unescaped_len);
+        (*dst)[unescaped_len] = '\0';
+      }
+      break;
+    }
+    case 'H': {
+      char **dst = (char **) info->user_data;
+      int i, len = token->len / 2;
+      *(int *) info->target = len;
+      if ((*dst = (char *) malloc(len + 1)) != NULL) {
+        for (i = 0; i < len; i++) {
+          (*dst)[i] = hexdec(token->ptr + 2 * i);
+        }
+        (*dst)[len] = '\0';
+        info->num_conversions++;
+      }
+      break;
+    }
+    case 'V': {
+      char **dst = (char **) info->target;
+      int len = token->len * 4 / 3 + 2;
+      if ((*dst = (char *) malloc(len + 1)) != NULL) {
+        int n = b64dec(token->ptr, token->len, *dst);
+        (*dst)[n] = '\0';
+        *(int *) info->user_data = n;
+        info->num_conversions++;
+      }
+      break;
+    }
+    case 'T':
+      info->num_conversions++;
+      *(struct json_token *) info->target = *token;
+      break;
+    default:
+      info->num_conversions += sscanf(token->ptr, info->fmt, info->target);
+      break;
+  }
+}
+
+int json_vscanf(const char *s, int len, const char *fmt, va_list ap) WEAK;
+int json_vscanf(const char *s, int len, const char *fmt, va_list ap) {
+  char path[JSON_MAX_PATH_LEN] = "", fmtbuf[20];
+  int i = 0;
+  char *p = NULL;
+  struct json_scanf_info info = {0, path, fmtbuf, NULL, NULL, 0};
+
+  while (fmt[i] != '\0') {
+    if (fmt[i] == '{') {
+      strcat(path, ".");
+      i++;
+    } else if (fmt[i] == '}') {
+      if ((p = strrchr(path, '.')) != NULL) *p = '\0';
+      i++;
+    } else if (fmt[i] == '%') {
+      info.target = va_arg(ap, void *);
+      info.type = fmt[i + 1];
+      switch (fmt[i + 1]) {
+        case 'M':
+        case 'V':
+        case 'H':
+          info.user_data = va_arg(ap, void *);
+        /* FALLTHROUGH */
+        case 'B':
+        case 'Q':
+        case 'T':
+          i += 2;
+          break;
+        default: {
+          const char *delims = ", \t\r\n]}";
+          int conv_len = strcspn(fmt + i + 1, delims) + 1;
+          snprintf(fmtbuf, sizeof(fmtbuf), "%.*s", conv_len, fmt + i);
+          i += conv_len;
+          i += strspn(fmt + i, delims);
+          break;
+        }
+      }
+      json_walk(s, len, json_scanf_cb, &info);
+    } else if (is_alpha(fmt[i]) || get_utf8_char_len(fmt[i]) > 1) {
+      const char *delims = ": \r\n\t";
+      int key_len = strcspn(&fmt[i], delims);
+      if ((p = strrchr(path, '.')) != NULL) p[1] = '\0';
+      sprintf(path + strlen(path), "%.*s", key_len, &fmt[i]);
+      i += key_len + strspn(fmt + i + key_len, delims);
+    } else {
+      i++;
+    }
+  }
+  return info.num_conversions;
+}
+
+int json_scanf(const char *str, int len, const char *fmt, ...) WEAK;
+int json_scanf(const char *str, int len, const char *fmt, ...) {
+  int result;
+  va_list ap;
+  va_start(ap, fmt);
+  result = json_vscanf(str, len, fmt, ap);
+  va_end(ap);
+  return result;
+}

src/frozen/frozen.h

@@ -0,0 +1,214 @@
+/*
+ * Copyright (c) 2004-2013 Sergey Lyubka <valenok@gmail.com>
+ * Copyright (c) 2013 Cesanta Software Limited
+ * All rights reserved
+ *
+ * This library is dual-licensed: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation. For the terms of this
+ * license, see <http: *www.gnu.org/licenses/>.
+ *
+ * You are free to use this library under the terms of the GNU General
+ * Public License, but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * Alternatively, you can license this library under a commercial
+ * license, as set out in <http://cesanta.com/products.html>.
+ */
+
+#ifndef CS_FROZEN_FROZEN_H_
+#define CS_FROZEN_FROZEN_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdio.h>
+
+/* JSON token type */
+enum json_token_type {
+  JSON_TYPE_INVALID = 0, /* memsetting to 0 should create INVALID value */
+  JSON_TYPE_STRING,
+  JSON_TYPE_NUMBER,
+  JSON_TYPE_TRUE,
+  JSON_TYPE_FALSE,
+  JSON_TYPE_NULL,
+  JSON_TYPE_OBJECT_START,
+  JSON_TYPE_OBJECT_END,
+  JSON_TYPE_ARRAY_START,
+  JSON_TYPE_ARRAY_END,
+
+  JSON_TYPES_CNT
+};
+
+/*
+ * Structure containing token type and value. Used in `json_walk()` and
+ * `json_scanf()` with the format specifier `%T`.
+ */
+struct json_token {
+  const char *ptr;           /* Points to the beginning of the value */
+  int len;                   /* Value length */
+  enum json_token_type type; /* Type of the token, possible values are above */
+};
+
+#define JSON_INVALID_TOKEN \
+  { 0, 0, JSON_TYPE_INVALID }
+
+/* Error codes */
+#define JSON_STRING_INVALID -1
+#define JSON_STRING_INCOMPLETE -2
+
+/*
+ * Callback-based SAX-like API.
+ *
+ * Property name and length is given only if it's available: i.e. if current
+ * event is an object's property. In other cases, `name` is `NULL`. For
+ * example, name is never given:
+ *   - For the first value in the JSON string;
+ *   - For events JSON_TYPE_OBJECT_END and JSON_TYPE_ARRAY_END
+ *
+ * E.g. for the input `{ "foo": 123, "bar": [ 1, 2, { "baz": true } ] }`,
+ * the sequence of callback invocations will be as follows:
+ *
+ * - type: JSON_TYPE_OBJECT_START, name: NULL, path: "", value: NULL
+ * - type: JSON_TYPE_NUMBER, name: "foo", path: ".foo", value: "123"
+ * - type: JSON_TYPE_ARRAY_START,  name: "bar", path: ".bar", value: NULL
+ * - type: JSON_TYPE_NUMBER, name: "0", path: ".bar[0]", value: "1"
+ * - type: JSON_TYPE_NUMBER, name: "1", path: ".bar[1]", value: "2"
+ * - type: JSON_TYPE_OBJECT_START, name: "2", path: ".bar[2]", value: NULL
+ * - type: JSON_TYPE_TRUE, name: "baz", path: ".bar[2].baz", value: "true"
+ * - type: JSON_TYPE_OBJECT_END, name: NULL, path: ".bar[2]", value: "{ \"baz\":
+ *true }"
+ * - type: JSON_TYPE_ARRAY_END, name: NULL, path: ".bar", value: "[ 1, 2, {
+ *\"baz\": true } ]"
+ * - type: JSON_TYPE_OBJECT_END, name: NULL, path: "", value: "{ \"foo\": 123,
+ *\"bar\": [ 1, 2, { \"baz\": true } ] }"
+ */
+typedef void (*json_walk_callback_t)(void *callback_data, const char *name,
+                                     size_t name_len, const char *path,
+                                     const struct json_token *token);
+
+/*
+ * Parse `json_string`, invoking `callback` in a way similar to SAX parsers;
+ * see `json_walk_callback_t`.
+ */
+int json_walk(const char *json_string, int json_string_length,
+              json_walk_callback_t callback, void *callback_data);
+
+/*
+ * JSON generation API.
+ * struct json_out abstracts output, allowing alternative printing plugins.
+ */
+struct json_out {
+  int (*printer)(struct json_out *, const char *str, size_t len);
+  union {
+    struct {
+      char *buf;
+      size_t size;
+      size_t len;
+    } buf;
+    void *data;
+    FILE *fp;
+  } u;
+};
+
+extern int json_printer_buf(struct json_out *, const char *, size_t);
+extern int json_printer_file(struct json_out *, const char *, size_t);
+
+#define JSON_OUT_BUF(buf, len) \
+  {                            \
+    json_printer_buf, {        \
+      { buf, len, 0 }          \
+    }                          \
+  }
+#define JSON_OUT_FILE(fp)   \
+  {                         \
+    json_printer_file, {    \
+      { (void *) fp, 0, 0 } \
+    }                       \
+  }
+
+typedef int (*json_printf_callback_t)(struct json_out *, va_list *ap);
+
+/*
+ * Generate formatted output into a given sting buffer.
+ * This is a superset of printf() function, with extra format specifiers:
+ *  - `%B` print json boolean, `true` or `false`. Accepts an `int`.
+ *  - `%Q` print quoted escaped string or `null`. Accepts a `const char *`.
+ *  - `%.*Q` same as `%Q`, but with length. Accepts `int`, `const char *`
+ *  - `%V` print quoted base64-encoded string. Accepts a `const char *`, `int`.
+ *  - `%H` print quoted hex-encoded string. Accepts a `int`, `const char *`.
+ *  - `%M` invokes a json_printf_callback_t function. That callback function
+ *  can consume more parameters.
+ *
+ * Return number of bytes printed. If the return value is bigger then the
+ * supplied buffer, that is an indicator of overflow. In the overflow case,
+ * overflown bytes are not printed.
+ */
+int json_printf(struct json_out *, const char *fmt, ...);
+int json_vprintf(struct json_out *, const char *fmt, va_list ap);
+
+/*
+ * Helper %M callback that prints contiguous C arrays.
+ * Consumes void *array_ptr, size_t array_size, size_t elem_size, char *fmt
+ * Return number of bytes printed.
+ */
+int json_printf_array(struct json_out *, va_list *ap);
+
+/*
+ * Scan JSON string `str`, performing scanf-like conversions according to `fmt`.
+ * This is a `scanf()` - like function, with following differences:
+ *
+ * 1. Object keys in the format string may be not quoted, e.g. "{key: %d}"
+ * 2. Order of keys in an object is irrelevant.
+ * 3. Several extra format specifiers are supported:
+ *    - %B: consumes `int *`, expects boolean `true` or `false`.
+ *    - %Q: consumes `char **`, expects quoted, JSON-encoded string. Scanned
+ *       string is malloc-ed, caller must free() the string.
+ *    - %V: consumes `char **`, `int *`. Expects base64-encoded string.
+ *       Result string is base64-decoded, malloced and NUL-terminated.
+ *       The length of result string is stored in `int *` placeholder.
+ *       Caller must free() the result.
+ *    - %H: consumes `int *`, `char **`.
+ *       Expects a hex-encoded string, e.g. "fa014f".
+ *       Result string is hex-decoded, malloced and NUL-terminated.
+ *       The length of the result string is stored in `int *` placeholder.
+ *       Caller must free() the result.
+ *    - %M: consumes custom scanning function pointer and
+ *       `void *user_data` parameter - see json_scanner_t definition.
+ *    - %T: consumes `struct json_token *`, fills it out with matched token.
+ *
+ * Return number of elements successfully scanned & converted.
+ * Negative number means scan error.
+ */
+int json_scanf(const char *str, int str_len, const char *fmt, ...);
+int json_vscanf(const char *str, int str_len, const char *fmt, va_list ap);
+
+/* json_scanf's %M handler  */
+typedef void (*json_scanner_t)(const char *str, int len, void *user_data);
+
+/*
+ * Helper function to scan array item with given path and index.
+ * Fills `token` with the matched JSON token.
+ * Return 0 if no array element found, otherwise non-0.
+ */
+int json_scanf_array_elem(const char *s, int len, const char *path, int index,
+                          struct json_token *token);
+
+/*
+ * Unescape JSON-encoded string src,slen into dst, dlen.
+ * src and dst may overlap.
+ * If destination buffer is too small (or zero-length), result string is not
+ * written but the length is counted nevertheless (similar to snprintf).
+ * Return the length of unescaped string in bytes.
+ */
+int json_unescape(const char *src, int slen, char *dst, int dlen);
+
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+
+#endif /* CS_FROZEN_FROZEN_H_ */