mirror of
https://github.com/panzi/mediaextract
synced 2025-02-26 09:40:36 +00:00
90 lines
2.4 KiB
C
90 lines
2.4 KiB
C
#include "it.h"
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int it_isfile(const uint8_t *data, size_t input_len, size_t *lengthptr)
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{
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if (input_len < IT_HEADER_SIZE)
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return 0;
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if (MAGIC(data) != IT_MAGIC || !probalby_mod_text(data + 4, 26))
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return 0;
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uint16_t orders = le16toh(*(uint16_t *)(data + 0x20));
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uint16_t instruments = le16toh(*(uint16_t *)(data + 0x22));
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uint16_t samples = le16toh(*(uint16_t *)(data + 0x24));
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uint16_t patterns = le16toh(*(uint16_t *)(data + 0x26));
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size_t length = IT_HEADER_SIZE + orders + instruments * 4 + samples * 4 + patterns * 4;
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if (input_len < length)
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return 0;
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#define UPDATE_LENGTH(len) \
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{ \
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size_t _len = (len); \
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if (_len > length) \
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{ \
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length = _len; \
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if (input_len < length) \
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return 0; \
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} \
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}
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/* scan instruments */
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for (const uint32_t *para = (const uint32_t *)(data + IT_HEADER_SIZE + orders),
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*para_end = para + instruments;
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para < para_end; ++ para)
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{
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size_t off = (size_t)le32toh(*para);
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UPDATE_LENGTH(off + IT_INSTRUMENT_SIZE);
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}
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/* scan samples */
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for (const uint32_t *para = (const uint32_t *)(data + IT_HEADER_SIZE + orders + instruments * 4),
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*para_end = para + samples;
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para < para_end; ++ para)
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{
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size_t off = (size_t)le32toh(*para);
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const unsigned char *ptr = data + off;
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UPDATE_LENGTH(off + IT_SAMPLE_HEADER_SIZE);
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if (MAGIC(ptr) != IT_SAMPLE_MAGIC)
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continue;
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uint32_t sample_length = le32toh(*(uint32_t *)(ptr + 0x30));
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uint32_t sample_pointer = le32toh(*(uint32_t *)(ptr + 0x48));
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if (sample_length && sample_pointer)
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{
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size_t sample_end = sample_pointer + sample_length;
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// there are some IT files out there with truncated samples:
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if (sample_end > input_len) sample_end = input_len;
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if (sample_end > length) length = sample_end;
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}
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}
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/* scan patterns */
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for (const uint32_t *para = (const uint32_t *)(data + IT_HEADER_SIZE + orders + instruments * 4 + samples * 4),
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*para_end = para + patterns;
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para < para_end; ++ para)
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{
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size_t off = (size_t)le32toh(*para);
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const unsigned char *ptr = data + off;
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UPDATE_LENGTH(off + IT_PATTERN_HEADER_SIZE);
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uint16_t pattern_length = le32toh(*(uint16_t *)ptr);
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size_t pattern_end = off + IT_PATTERN_HEADER_SIZE + pattern_length;
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// there are some IT files out there with truncated patterns:
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if (pattern_end > input_len) pattern_end = input_len;
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if (pattern_end > length) length = pattern_end;
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}
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if (lengthptr) *lengthptr = length;
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return 1;
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}
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