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Added functions for finding data forwards and backwards in a stream.

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This commit is contained in:
Nathan Moinvaziri 2018-11-07 20:23:42 -08:00
parent e39032376e
commit 65dbda889d
2 changed files with 115 additions and 0 deletions
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113
mz_strm.c
View File

@ -233,6 +233,119 @@ int32_t mz_stream_seek(void *stream, int64_t offset, int32_t origin)
return strm->vtbl->seek(strm, offset, origin);
}
int32_t mz_stream_find(void *stream, const void *find, int32_t find_size, int64_t max_seek, int64_t *position)
{
uint8_t buf[1024];
int32_t read_size = sizeof(buf);
int64_t read_pos = 0;
int64_t start_pos = 0;
int64_t disk_offset = 0;
int32_t i = 0;
int32_t err = MZ_OK;
if (stream == NULL || find == NULL || position == NULL)
return MZ_PARAM_ERROR;
if (find_size < 0 || find_size >= sizeof(buf))
return MZ_PARAM_ERROR;
*position = 0;
start_pos = mz_stream_tell(stream);
while (max_seek > 0)
{
if (read_size > max_seek)
read_size = (int32_t)max_seek;
if (mz_stream_read(stream, buf, read_size) != read_size)
break;
for (i = 0; i < read_size - find_size; i += 1)
{
if (memcmp(&buf[i], find, find_size) != 0)
continue;
// Seek to position on disk where the data was found
disk_offset = mz_stream_tell(stream);
err = mz_stream_seek(stream, disk_offset - (read_size - i), MZ_SEEK_SET);
if (err != MZ_OK)
return MZ_EXIST_ERROR;
*position = start_pos + read_pos + i;
return MZ_OK;
}
read_pos += read_size;
if (read_size == sizeof(buf))
read_size -= find_size;
memcpy(buf + read_size, buf, find_size);
max_seek -= read_size;
}
return MZ_EXIST_ERROR;
}
int32_t mz_stream_find_reverse(void *stream, const void *find, int32_t find_size, int64_t max_seek, int64_t *position)
{
uint8_t buf[1024];
int64_t read_total = 0;
int32_t read_size = sizeof(buf);
int64_t read_pos = 0;
int64_t start_pos = 0;
int64_t disk_pos = 0;
int32_t i = 0;
int32_t err = MZ_OK;
if (stream == NULL || find == NULL || position == NULL)
return MZ_PARAM_ERROR;
if (find_size < 0 || find_size >= sizeof(buf))
return MZ_PARAM_ERROR;
*position = 0;
start_pos = mz_stream_tell(stream);
while (read_total < max_seek)
{
read_total += read_size;
if (read_total > max_seek)
read_total = max_seek;
read_pos = start_pos - read_total;
if (read_size > (start_pos - read_pos))
read_size = (int32_t)(start_pos - read_pos);
if (mz_stream_seek(stream, read_pos, MZ_SEEK_SET) != MZ_OK)
break;
if (mz_stream_read(stream, buf, read_size) != read_size)
break;
for (i = read_size - find_size; i >= 0; i -= 1)
{
if (memcmp(&buf[i], find, find_size) != 0)
continue;
// Seek to position on disk where the data was found
disk_pos = mz_stream_tell(stream);
err = mz_stream_seek(stream, (disk_pos - read_size) + i, MZ_SEEK_SET);
if (err != MZ_OK)
return MZ_EXIST_ERROR;
*position = read_pos + i;
return MZ_OK;
}
if (read_size == sizeof(buf))
read_size -= find_size;
}
return MZ_EXIST_ERROR;
}
int32_t mz_stream_close(void *stream)
{
mz_stream *strm = (mz_stream *)stream;

2
mz_strm.h
View File

@ -92,6 +92,8 @@ int32_t mz_stream_copy(void *target, void *source, int32_t len);
int32_t mz_stream_copy_stream(void *target, mz_stream_write_cb write_cb, void *source, mz_stream_read_cb read_cb, int32_t len);
int64_t mz_stream_tell(void *stream);
int32_t mz_stream_seek(void *stream, int64_t offset, int32_t origin);
int32_t mz_stream_find(void *stream, const void *find, int32_t find_size, int64_t max_seek, int64_t *position);
int32_t mz_stream_find_reverse(void *stream, const void *find, int32_t find_size, int64_t max_seek, int64_t *position);
int32_t mz_stream_close(void *stream);
int32_t mz_stream_error(void *stream);