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Add ffi/pointer-buffer for easier memory manipulation in FFI.

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Added underlying buffer support for buffer instances that cannot
reallocated underlying memory - useful for (small) memory mapped
files and other FFI utilties.
This commit is contained in:
Calvin Rose
2023-02-12 09:03:31 -06:00
parent d1eba60ba8
commit 1cadff8e58
3 changed files with 42 additions and 5 deletions
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14
src/core/buffer.c
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@@ -28,6 +28,13 @@
#include "state.h"
#endif
/* Allow for managed buffers that cannot realloc/free their backing memory */
static void janet_buffer_can_realloc(JanetBuffer *buffer) {
if (buffer->gc.flags & JANET_BUFFER_FLAG_NO_REALLOC) {
janet_panic("buffer cannot reallocate foreign memory");
}
}
/* Initialize a buffer */
static JanetBuffer *janet_buffer_init_impl(JanetBuffer *buffer, int32_t capacity) {
uint8_t *data = NULL;
@@ -53,7 +60,9 @@ JanetBuffer *janet_buffer_init(JanetBuffer *buffer, int32_t capacity) {
/* Deinitialize a buffer (free data memory) */
void janet_buffer_deinit(JanetBuffer *buffer) {
janet_free(buffer->data);
if (!(buffer->gc.flags & JANET_BUFFER_FLAG_NO_REALLOC)) {
janet_free(buffer->data);
}
}
/* Initialize a buffer */
@@ -67,6 +76,7 @@ void janet_buffer_ensure(JanetBuffer *buffer, int32_t capacity, int32_t growth)
uint8_t *new_data;
uint8_t *old = buffer->data;
if (capacity <= buffer->capacity) return;
janet_buffer_can_realloc(buffer);
int64_t big_capacity = ((int64_t) capacity) * growth;
capacity = big_capacity > INT32_MAX ? INT32_MAX : (int32_t) big_capacity;
janet_gcpressure(capacity - buffer->capacity);
@@ -99,6 +109,7 @@ void janet_buffer_extra(JanetBuffer *buffer, int32_t n) {
}
int32_t new_size = buffer->count + n;
if (new_size > buffer->capacity) {
janet_buffer_can_realloc(buffer);
int32_t new_capacity = (new_size > (INT32_MAX / 2)) ? INT32_MAX : (new_size * 2);
uint8_t *new_data = janet_realloc(buffer->data, new_capacity * sizeof(uint8_t));
janet_gcpressure(new_capacity - buffer->capacity);
@@ -220,6 +231,7 @@ JANET_CORE_FN(cfun_buffer_trim,
"modified buffer.") {
janet_fixarity(argc, 1);
JanetBuffer *buffer = janet_getbuffer(argv, 0);
janet_buffer_can_realloc(buffer);
if (buffer->count < buffer->capacity) {
int32_t newcap = buffer->count > 4 ? buffer->count : 4;
uint8_t *newData = janet_realloc(buffer->data, newcap);