65 lines
1.9 KiB
Go
65 lines
1.9 KiB
Go
package coding
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import (
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"fmt"
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"io"
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)
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// base64CleanerTable notes byte values that should be stripped (-2), stripped w/ error (-1).
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var base64CleanerTable = []int8{
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
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52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,
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-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
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15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
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-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
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41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
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}
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// Base64Cleaner improves the tolerance of in Go's built-in base64 decoder by stripping out
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// characters that would cause decoding to fail.
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type Base64Cleaner struct {
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// Report of non-whitespace characters detected while cleaning base64 data.
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Errors []error
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r io.Reader
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buffer [1024]byte
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}
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// Enforce io.Reader interface.
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var _ io.Reader = &Base64Cleaner{}
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// NewBase64Cleaner returns a Base64Cleaner object for the specified reader. Base64Cleaner
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// implements the io.Reader interface.
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func NewBase64Cleaner(r io.Reader) *Base64Cleaner {
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return &Base64Cleaner{
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Errors: make([]error, 0),
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r: r,
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}
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}
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// Read method for io.Reader interface.
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func (bc *Base64Cleaner) Read(p []byte) (n int, err error) {
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// Size our buf to smallest of len(p) or len(bc.buffer).
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size := len(bc.buffer)
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if size > len(p) {
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size = len(p)
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}
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buf := bc.buffer[:size]
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bn, err := bc.r.Read(buf)
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for i := 0; i < bn; i++ {
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switch base64CleanerTable[buf[i]&0x7f] {
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case -2:
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// Strip these silently: tab, \n, \r, space, equals sign.
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case -1:
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// Strip these, but warn the client.
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bc.Errors = append(bc.Errors, fmt.Errorf("unexpected %q in base64 stream", buf[i]))
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default:
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p[n] = buf[i]
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n++
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}
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}
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return
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}
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