mirror of https://git.ffmpeg.org/ffmpeg.git
avformat/matroskaenc: Refactor writing EBML lengths
This commit factors the ability to write ordinary EBML numbers out of the functions for writing EBML lengths. This is in preparation for future commits. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
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@ -189,18 +189,37 @@ static void put_ebml_size_unknown(AVIOContext *pb, int bytes)
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ffio_fill(pb, 0xff, bytes - 1);
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}
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/**
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* Returns how many bytes are needed to represent a number
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* as EBML variable length integer.
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*/
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static int ebml_num_size(uint64_t num)
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{
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int bytes = 0;
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do {
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bytes++;
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} while (num >>= 7);
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return bytes;
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}
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/**
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* Calculate how many bytes are needed to represent the length field
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* of an EBML element whose payload has a given length.
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*/
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static int ebml_length_size(uint64_t length)
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{
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int bytes = 0;
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length++;
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do {
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bytes++;
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} while (length >>= 7);
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return bytes;
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return ebml_num_size(length + 1);
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}
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/**
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* Write a number as EBML variable length integer on `bytes` bytes.
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* `bytes` is taken literally without checking.
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*/
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static void put_ebml_num(AVIOContext *pb, uint64_t num, int bytes)
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{
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num |= 1ULL << bytes * 7;
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for (int i = bytes - 1; i >= 0; i--)
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avio_w8(pb, (uint8_t)(num >> i * 8));
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}
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/**
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@ -211,7 +230,7 @@ static int ebml_length_size(uint64_t length)
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*/
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static void put_ebml_length(AVIOContext *pb, uint64_t length, int bytes)
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{
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int i, needed_bytes = ebml_length_size(length);
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int needed_bytes = ebml_length_size(length);
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// sizes larger than this are currently undefined in EBML
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av_assert0(length < (1ULL << 56) - 1);
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@ -221,10 +240,7 @@ static void put_ebml_length(AVIOContext *pb, uint64_t length, int bytes)
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// The bytes needed to write the given size must not exceed
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// the bytes that we ought to use.
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av_assert0(bytes >= needed_bytes);
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length |= 1ULL << bytes * 7;
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for (i = bytes - 1; i >= 0; i--)
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avio_w8(pb, (uint8_t)(length >> i * 8));
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put_ebml_num(pb, length, bytes);
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}
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/**
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