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Rewrite file hasher to limit amount hashed

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== DETAILS
Since the content file could potentially be huge, hashing the
whole thing at runtime may take a really long time. Plus, it
was loading the whole file into RAM at once.

Now, we only load 1MB at a time and hash up to the first 64MB.

== TESTING
I don't have any large content files to test it with, but I
tested it with a small one and confirmed that the hash was
correct.
This commit is contained in:
Nathan Strong 2018-10-18 16:38:02 -07:00
parent edacf67e75
commit d03c0be71d
1 changed files with 40 additions and 7 deletions
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47
libretro-common/encodings/encoding_crc32.c
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@ -91,17 +91,50 @@ uint32_t encoding_crc32(uint32_t crc, const uint8_t *buf, size_t len)
return crc ^ 0xffffffff;
}
#define CRC32_BUFFER_SIZE 1048576
#define CRC32_MAX_MB 64
/**
* Calculate a CRC32 from the first part of the given file.
* "first part" being the first (CRC32_BUFFER_SIZE * CRC32_MAX_MB)
* bytes.
* TODO: maybe make these numbers configurable?
*
* Returns: the crc32, or 0 if there was an error.
*/
uint32_t file_crc32(uint32_t crc, const char *path) {
if(path == NULL)
return 0;
void *file_bytes = NULL;
int64_t file_len = 0;
RFILE *file = NULL;
unsigned char *buf = NULL;
int i, nread;
if(filestream_read_file(path, &file_bytes, &file_len)) {
crc = encoding_crc32(crc, (uint8_t *)file_bytes, file_len);
free(file_bytes);
return crc;
file = filestream_open(path, RETRO_VFS_FILE_ACCESS_READ, 0);
if(file == NULL)
goto error;
buf = (char *)malloc(CRC32_BUFFER_SIZE);
if(buf == NULL)
goto error;
for(i = 0; i < CRC32_MAX_MB; i++) {
nread = filestream_read(file, buf, CRC32_BUFFER_SIZE);
if(nread < 0)
goto error;
crc = encoding_crc32(crc, buf, nread);
if(filestream_eof(file))
break;
}
return 0;
free(buf);
filestream_close(file);
return crc;
error:
if(buf)
free(buf);
if(file)
filestream_close(file);
return 0;
}