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add int/to-bytes

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int/to-bytes unpacks the bytes of a 64-bit integer into a tuple.
This commit is contained in:
Ian Shehadeh 2022-03-04 08:48:54 -05:00
parent 56ba1d9cd3
commit 6aea7c7f70
2 changed files with 59 additions and 0 deletions
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38
src/core/inttypes.c
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@ -238,6 +238,43 @@ JANET_CORE_FN(cfun_to_number,
janet_panicf("expected int/u64 or int/s64, got %q", argv[0]);
}
JANET_CORE_FN(cfun_to_bytes,
"(int/to-bytes value &opt endianness)",
"Convert an `int/s64` or `int/u64` into an 8-element tuple of bytes.\n"
"the endianness paramater indicates the byte order:\n"
"- `nil` (unset): system byte order\n"
"- `:le`: little-endian, least significant byte first\n"
"- `:be`: big-endian, most significant byte first\n") {
janet_arity(argc, 1, 2);
if (janet_is_int(argv[0]) == JANET_INT_NONE) {
janet_panicf("int/to-bytes: expected an int/s64 or int/u64, got %q", argv[0]);
}
int reverse = 0;
if (argc > 1 && !janet_checktype(argv[1], JANET_NIL)) {
JanetKeyword endianness_kw = janet_getkeyword(argv, 1);
if (!janet_cstrcmp(endianness_kw, "le")) {
#if JANET_BIG_ENDIAN
reverse = 1;
#endif
} else if (!janet_cstrcmp(endianness_kw, "be")) {
#if JANET_LITTLE_ENDIAN
reverse = 1;
#endif
} else {
janet_panicf("int/to-bytes: expected endianness :le, :be or nil, got %v", argv[1]);
}
}
uint8_t *bytes = janet_unwrap_abstract(argv[0]);
Janet *bytes_tuple = janet_tuple_begin(8);
for (int i = 0; i < 8; ++i) {
bytes_tuple[i] = janet_wrap_integer(bytes[reverse ? 7 - i : i]);
}
return janet_wrap_tuple(janet_tuple_end(bytes_tuple));
}
/*
* Code to support polymorphic comparison.
* int/u64 and int/s64 support a "compare" method that allows
@ -546,6 +583,7 @@ void janet_lib_inttypes(JanetTable *env) {
JANET_CORE_REG("int/s64", cfun_it_s64_new),
JANET_CORE_REG("int/u64", cfun_it_u64_new),
JANET_CORE_REG("int/to-number", cfun_to_number),
JANET_CORE_REG("int/to-bytes", cfun_to_bytes),
JANET_REG_END
};
janet_core_cfuns_ext(env, NULL, it_cfuns);

21
test/suite0006.janet
View File

@ -91,6 +91,27 @@
"trap INT64_MIN / -1"
(:/ (int/s64 "-0x8000_0000_0000_0000") -1))
# int/s64 and int/u64 serialization
(assert (= (int/to-bytes (u64 0)) [0 0 0 0 0 0 0 0]))
(assert (= (int/to-bytes (i64 1) :le) [1 0 0 0 0 0 0 0]))
(assert (= (int/to-bytes (i64 1) :be) [0 0 0 0 0 0 0 1]))
(assert (= (int/to-bytes (i64 -1)) [0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF]))
(assert (= (int/to-bytes (i64 -5) :be) [0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF (- 0xFF 4)]))
(assert (= (int/to-bytes (u64 1) :le) [1 0 0 0 0 0 0 0]))
(assert (= (int/to-bytes (u64 1) :be) [0 0 0 0 0 0 0 1]))
(assert (= (int/to-bytes (u64 300) :be) [0 0 0 0 0 0 0x01 0x2C]))
(assert-error
"bad value passed to int/to-bytes"
(int/to-bytes 1))
(assert-error
"invalid endianness passed to int/to-bytes"
(int/to-bytes (u64 0) :little))
# Dynamic bindings
(setdyn :a 10)
(assert (= 40 (with-dyns [:a 25 :b 15] (+ (dyn :a) (dyn :b)))) "dyn usage 1")