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60 lines
1.7 KiB
60 lines
1.7 KiB
package bin |
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import "io" |
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const ( |
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// If L <= 253, the serialization contains one byte with the value of L, |
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// then L bytes of the string followed by 0 to 3 characters containing 0, |
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// such that the overall length of the value be divisible by 4, |
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// whereupon all of this is interpreted as a sequence of int(L/4)+1 32-bit numbers. |
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maxSmallStringLength = 253 |
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// If L >= 254, the serialization contains byte 254, followed by 3 bytes with |
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// the string length L, followed by L bytes of the string, further followed |
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// by 0 to 3 null padding bytes. |
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firstLongStringByte = 254 |
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) |
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func encodeString(b []byte, v string) []byte { |
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l := len(v) |
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if l <= maxSmallStringLength { |
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b = append(b, byte(l)) |
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b = append(b, v...) |
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currentLen := l + 1 |
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b = append(b, make([]byte, nearestPaddedValueLength(currentLen)-currentLen)...) |
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return b |
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} |
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b = append(b, firstLongStringByte, byte(l), byte(l>>8), byte(l>>16)) |
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b = append(b, v...) |
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currentLen := l + 4 |
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b = append(b, make([]byte, nearestPaddedValueLength(currentLen)-currentLen)...) |
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return b |
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} |
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func decodeString(b []byte) (padding int, v string, err error) { |
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if len(b) == 0 { |
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return 0, "", io.ErrUnexpectedEOF |
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} |
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if b[0] == firstLongStringByte { |
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if len(b) < 4 { |
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return 0, "", io.ErrUnexpectedEOF |
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} |
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strLen := uint32(b[1]) | uint32(b[2])<<8 | uint32(b[3])<<16 |
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if len(b) < (int(strLen) + 4) { |
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return 0, "", io.ErrUnexpectedEOF |
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} |
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return nearestPaddedValueLength(int(strLen) + 4), string(b[4 : strLen+4]), nil |
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} |
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strLen := int(b[0]) |
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if len(b) < (strLen + 1) { |
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return 0, "", io.ErrUnexpectedEOF |
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} |
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if strLen > maxSmallStringLength { |
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return 0, "", &InvalidLengthError{ |
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Length: strLen, |
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Where: "string", |
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} |
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} |
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return nearestPaddedValueLength(strLen + 1), string(b[1 : strLen+1]), nil |
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}
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