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63 lines
1.5 KiB
63 lines
1.5 KiB
package util |
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import ( |
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"encoding/binary" |
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) |
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// got the logic from: https://github.com/bogem/id3v2 , thank you very much. |
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const first7BitsMask = uint32(254 << 24) // shifting 11111110 to the end of uint32 |
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// Converts given bytes into integer |
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func BytesToInt(gBytes []byte) uint32 { |
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var integer uint32 = 0 |
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for _, b := range gBytes { |
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integer = integer << 8 |
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integer = integer | uint32(b) |
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} |
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return integer |
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} |
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// Simply converts given uint32 into synch unsafe bytes |
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func IntToBytes(gInt uint32) []byte { |
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buff := make([]byte, 4) |
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binary.BigEndian.PutUint32(buff, gInt) |
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return buff |
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} |
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// Decodes given integer bytes into integer, ignores the first bit |
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// of every given byte in binary form |
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func BytesToIntSynchsafe(gBytes []byte) uint32 { |
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var integer uint32 = 0 |
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for _, b := range gBytes { |
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integer = integer << 7 |
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integer = integer | uint32(b) |
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} |
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return integer |
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} |
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// The exact opposite of what `BytesToIntSynchsafe` does |
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// Finally understood with the help of: https://github.com/bogem/id3v2/blob/master/size.go , |
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// thank you very much ! |
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func IntToBytesSynchsafe(gInt uint32) []byte { |
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var synchsafeIBytes []byte |
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// skip 4 0`ed bits |
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gInt = gInt << 4 |
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// int32 == 4 bytes |
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for i := 0; i < 32/8; i++ { |
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// get first 7 bits |
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first7Bits := gInt & first7BitsMask |
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// shift captured bits to the beginning |
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first7Bits = first7Bits >> (3*8 + 1) |
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b := byte(first7Bits) |
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synchsafeIBytes = append(synchsafeIBytes, b) |
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// prepare next 7 bits for the next iteration |
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gInt = gInt << 7 |
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} |
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return synchsafeIBytes |
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}
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