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//
// webpinfo.c: acquire information about WebP files in JSON format
//
// Copyright (c) 2021, Přemysl Eric Janouch <p@janouch.name>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
//
#include "info.h"
#include <jv.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// --- WebP --------------------------------------------------------------------
// https://github.com/webmproject/libwebp/blob/master/doc/webp-container-spec.txt
// https://github.com/webmproject/libwebp/blob/master/doc/webp-lossless-bitstream-spec.txt
// https://datatracker.ietf.org/doc/html/rfc6386
//
// Pretty versions, hopefully not outdated:
// https://developers.google.com/speed/webp/docs/riff_container
// https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification
static jv
parse_webp(jv o, const uint8_t *p, size_t len)
{
// libwebp won't let us simply iterate over all chunks, so handroll it.
if (len < 12 || memcmp(p, "RIFF", 4) || memcmp(p + 8, "WEBP", 4))
return add_error(o, "not a WEBP file");
// TODO(p): This can still be parseable.
// TODO(p): Warn on trailing data.
uint32_t size = u32le(p + 4);
if (8 + size < len)
return add_error(o, "truncated file");
const uint8_t *end = p + 8 + size;
p += 12;
jv chunks = jv_array();
while (p < end) {
if (end - p < 8) {
o = add_warning(o, "framing mismatch");
printf("%ld", end - p);
break;
}
uint32_t chunk_size = u32le(p + 4);
uint32_t chunk_advance = (chunk_size + 1) & ~1;
if (p + 8 + chunk_advance > end) {
o = add_warning(o, "runaway chunk payload");
break;
}
char fourcc[5] = "";
memcpy(fourcc, p, 4);
chunks = jv_array_append(chunks, jv_string(fourcc));
p += 8;
// TODO(p): Decode VP8 and VP8L chunk metadata.
if (!strcmp(fourcc, "EXIF"))
o = parse_exif(o, p, chunk_size);
if (!strcmp(fourcc, "ICCP"))
o = parse_icc(o, p, chunk_size);
p += chunk_advance;
}
return jv_set(o, jv_string("chunks"), chunks);
}
// --- I/O ---------------------------------------------------------------------
static jv
do_file(const char *filename, jv o)
{
const char *err = NULL;
FILE *fp = fopen(filename, "rb");
if (!fp) {
err = strerror(errno);
goto error;
}
uint8_t *data = NULL, buf[256 << 10];
size_t n, len = 0;
while ((n = fread(buf, sizeof *buf, sizeof buf / sizeof *buf, fp))) {
data = realloc(data, len + n);
memcpy(data + len, buf, n);
len += n;
}
if (ferror(fp)) {
err = strerror(errno);
goto error_read;
}
o = parse_webp(o, data, len);
error_read:
fclose(fp);
free(data);
error:
if (err)
o = add_error(o, err);
return o;
}
int
main(int argc, char *argv[])
{
(void) parse_psir;
// XXX: Can't use `xargs -P0`, there's a risk of non-atomic writes.
// Usage: find . -iname *.png -print0 | xargs -0 ./pnginfo
for (int i = 1; i < argc; i++) {
const char *filename = argv[i];
jv o = jv_object();
o = jv_object_set(o, jv_string("filename"), jv_string(filename));
o = do_file(filename, o);
jv_dumpf(o, stdout, 0 /* Might consider JV_PRINT_SORTED. */);
fputc('\n', stdout);
}
return 0;
}
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