58 lines
2.0 KiB
Go
58 lines
2.0 KiB
Go
package sign
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import (
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"bytes"
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"fmt"
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"strings"
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)
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func (context *SignContext) updateByteRange() error {
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if _, err := context.OutputBuffer.Seek(0, 0); err != nil {
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return err
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}
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// Set ByteRangeValues by looking for the /Contents< filled with zeros
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contentsPlaceholder := bytes.Repeat([]byte("0"), int(context.SignatureMaxLength))
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contentsIndex := bytes.Index(context.OutputBuffer.Buff.Bytes(), contentsPlaceholder)
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if contentsIndex == -1 {
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return fmt.Errorf("failed to find contents placeholder")
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}
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// Calculate ByteRangeValues
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signatureContentsStart := int64(contentsIndex) - 1
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signatureContentsEnd := signatureContentsStart + int64(context.SignatureMaxLength) + 2
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context.ByteRangeValues = []int64{
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0,
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signatureContentsStart,
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signatureContentsEnd,
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int64(context.OutputBuffer.Buff.Len()) - signatureContentsEnd,
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}
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new_byte_range := fmt.Sprintf("/ByteRange [%d %d %d %d]", context.ByteRangeValues[0], context.ByteRangeValues[1], context.ByteRangeValues[2], context.ByteRangeValues[3])
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// Make sure our ByteRange string has the same length as the placeholder.
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if len(new_byte_range) < len(signatureByteRangePlaceholder) {
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new_byte_range += strings.Repeat(" ", len(signatureByteRangePlaceholder)-len(new_byte_range))
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} else if len(new_byte_range) != len(signatureByteRangePlaceholder) {
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return fmt.Errorf("new byte range string is the same lenght as the placeholder")
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}
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// Find the placeholder in the buffer
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placeholderIndex := bytes.Index(context.OutputBuffer.Buff.Bytes(), []byte(signatureByteRangePlaceholder))
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if placeholderIndex == -1 {
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return fmt.Errorf("failed to find ByteRange placeholder")
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}
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// Replace the placeholder with the new byte range
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bufferBytes := context.OutputBuffer.Buff.Bytes()
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copy(bufferBytes[placeholderIndex:placeholderIndex+len(new_byte_range)], []byte(new_byte_range))
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// Rewrite the buffer with the updated bytes
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context.OutputBuffer.Buff.Reset()
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if _, err := context.OutputBuffer.Buff.Write(bufferBytes); err != nil {
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return err
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}
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return nil
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}
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