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elinks/src/encoding/zstd.c
2022-02-21 16:21:29 +01:00

189 lines
3.6 KiB
C

/* zstd encoding (ENCODING_ZSTD) backend */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <zstd.h>
#include <errno.h>
#include "elinks.h"
#include "encoding/zstd.h"
#include "encoding/encoding.h"
#include "util/memory.h"
/* How many bytes of compressed data to read before decompressing.
*/
#define ELINKS_ZSTD_BUFFER_LENGTH 16384
struct zstd_enc_data {
ZSTD_DCtx *zstd_stream;
ZSTD_inBuffer input;
ZSTD_outBuffer output;
size_t sent_pos;
/* The file descriptor from which we read. */
int fdread;
int decoded:1;
};
static int
zstd_open(struct stream_encoded *stream, int fd)
{
struct zstd_enc_data *data = (struct zstd_enc_data *)mem_calloc(1, sizeof(*data));
stream->data = NULL;
if (!data) {
return -1;
}
data->fdread = fd;
data->zstd_stream = ZSTD_createDCtx();
if (!data->zstd_stream) {
mem_free(data);
return -1;
}
stream->data = data;
return 0;
}
static char *
zstd_decode_buffer(struct stream_encoded *st, char *data, int len, int *new_len)
{
struct zstd_enc_data *enc_data = (struct zstd_enc_data *)st->data;
int error;
*new_len = 0; /* default, left there if an error occurs */
enc_data->input.src = data;
enc_data->input.pos = 0;
enc_data->input.size = len;
enc_data->output.pos = 0;
enc_data->output.size = 0;
enc_data->output.dst = NULL;
do {
char *new_buffer;
size_t size = enc_data->output.size + ELINKS_ZSTD_BUFFER_LENGTH;
new_buffer = (char *)mem_realloc(enc_data->output.dst, size);
if (!new_buffer) {
error = 1;
break;
}
enc_data->output.dst = new_buffer;
enc_data->output.size += ELINKS_ZSTD_BUFFER_LENGTH;
error = ZSTD_decompressStream(enc_data->zstd_stream, &enc_data->output , &enc_data->input);
if (ZSTD_isError(error)) {
mem_free_if(enc_data->output.dst);
enc_data->output.dst = NULL;
return NULL;
}
} while (enc_data->input.pos < enc_data->input.size);
*new_len = enc_data->output.pos;
return (char *)enc_data->output.dst;
}
static int
zstd_read(struct stream_encoded *stream, char *buf, int len)
{
struct zstd_enc_data *data = (struct zstd_enc_data *) stream->data;
if (!data) return -1;
assert(len > 0);
if (!data->decoded) {
size_t read_pos = 0;
char *tmp_buf = (char *)mem_alloc(len);
int new_len;
if (!tmp_buf) {
return 0;
}
do {
int l = safe_read(data->fdread, tmp_buf + read_pos, len - read_pos);
if (!l) break;
if (l == -1 && errno == EAGAIN) {
continue;
}
if (l == -1) {
return -1;
}
read_pos += l;
} while (1);
if (zstd_decode_buffer(stream, tmp_buf, len, &new_len)) {
data->decoded = 1;
}
mem_free(tmp_buf);
}
if (data->decoded) {
int length = len < (data->output.pos - data->sent_pos) ? len : (data->output.pos - data->sent_pos);
if (length <= 0) {
mem_free(data->output.dst);
data->output.dst = NULL;
} else {
memcpy(buf, (void *)((char *)(data->output.dst) + data->sent_pos), length);
data->sent_pos += length;
}
return length;
}
return -1;
}
static void
zstd_close(struct stream_encoded *stream)
{
struct zstd_enc_data *data = (struct zstd_enc_data *) stream->data;
if (data) {
if (data->zstd_stream) {
ZSTD_freeDCtx(data->zstd_stream);
data->zstd_stream = NULL;
}
if (data->fdread != -1) {
close(data->fdread);
}
mem_free(data);
stream->data = 0;
}
}
const char *
get_zstd_version(void)
{
return ZSTD_versionString();
}
static const char *const zstd_extensions[] = { ".zst", NULL };
const struct decoding_backend zstd_decoding_backend = {
"zstd",
zstd_extensions,
zstd_open,
zstd_read,
zstd_decode_buffer,
zstd_close,
};