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// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package json
import "bytes"
// HTMLEscape appends to dst the JSON-encoded src with <, >, &, U+2028 and U+2029
// characters inside string literals changed to \u003c, \u003e, \u0026, \u2028, \u2029
// so that the JSON will be safe to embed inside HTML <script> tags.
// For historical reasons, web browsers don't honor standard HTML
// escaping within <script> tags, so an alternative JSON encoding must be used.
func HTMLEscape(dst *bytes.Buffer, src []byte) {
dst.Grow(len(src))
dst.Write(appendHTMLEscape(dst.AvailableBuffer(), src))
}
func appendHTMLEscape(dst, src []byte) []byte {
// The characters can only appear in string literals,
// so just scan the string one byte at a time.
start := 0
for i, c := range src {
if c == '<' || c == '>' || c == '&' {
dst = append(dst, src[start:i]...)
dst = append(dst, '\\', 'u', '0', '0', hex[c>>4], hex[c&0xF])
start = i + 1
}
// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).
if c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {
dst = append(dst, src[start:i]...)
dst = append(dst, '\\', 'u', '2', '0', '2', hex[src[i+2]&0xF])
start = i + len("\u2029")
}
}
return append(dst, src[start:]...)
}
// Compact appends to dst the JSON-encoded src with
// insignificant space characters elided.
func Compact(dst *bytes.Buffer, src []byte) error {
dst.Grow(len(src))
b := dst.AvailableBuffer()
b, err := appendCompact(b, src, false)
dst.Write(b)
return err
}
func appendCompact(dst, src []byte, escape bool) ([]byte, error) {
origLen := len(dst)
scan := newScanner()
defer freeScanner(scan)
start := 0
for i, c := range src {
if escape && (c == '<' || c == '>' || c == '&') {
if start < i {
dst = append(dst, src[start:i]...)
}
dst = append(dst, '\\', 'u', '0', '0', hex[c>>4], hex[c&0xF])
start = i + 1
}
// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).
if escape && c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {
if start < i {
dst = append(dst, src[start:i]...)
}
dst = append(dst, '\\', 'u', '2', '0', '2', hex[src[i+2]&0xF])
start = i + 3
}
v := scan.step(scan, c)
if v >= scanSkipSpace {
if v == scanError {
break
}
if start < i {
dst = append(dst, src[start:i]...)
}
start = i + 1
}
}
if scan.eof() == scanError {
return dst[:origLen], scan.err
}
if start < len(src) {
dst = append(dst, src[start:]...)
}
return dst, nil
}
func appendNewline(dst []byte, prefix, indent string, depth int) []byte {
dst = append(dst, '\n')
dst = append(dst, prefix...)
for i := 0; i < depth; i++ {
dst = append(dst, indent...)
}
return dst
}
// indentGrowthFactor specifies the growth factor of indenting JSON input.
// Empirically, the growth factor was measured to be between 1.4x to 1.8x
// for some set of compacted JSON with the indent being a single tab.
// Specify a growth factor slightly larger than what is observed
// to reduce probability of allocation in appendIndent.
// A factor no higher than 2 ensures that wasted space never exceeds 50%.
const indentGrowthFactor = 2
// Indent appends to dst an indented form of the JSON-encoded src.
// Each element in a JSON object or array begins on a new,
// indented line beginning with prefix followed by one or more
// copies of indent according to the indentation nesting.
// The data appended to dst does not begin with the prefix nor
// any indentation, to make it easier to embed inside other formatted JSON data.
// Although leading space characters (space, tab, carriage return, newline)
// at the beginning of src are dropped, trailing space characters
// at the end of src are preserved and copied to dst.
// For example, if src has no trailing spaces, neither will dst;
// if src ends in a trailing newline, so will dst.
func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error {
dst.Grow(indentGrowthFactor * len(src))
b := dst.AvailableBuffer()
b, err := appendIndent(b, src, prefix, indent)
dst.Write(b)
return err
}
func appendIndent(dst, src []byte, prefix, indent string) ([]byte, error) {
origLen := len(dst)
scan := newScanner()
defer freeScanner(scan)
needIndent := false
depth := 0
for _, c := range src {
scan.bytes++
v := scan.step(scan, c)
if v == scanSkipSpace {
continue
}
if v == scanError {
break
}
if needIndent && v != scanEndObject && v != scanEndArray {
needIndent = false
depth++
dst = appendNewline(dst, prefix, indent, depth)
}
// Emit semantically uninteresting bytes
// (in particular, punctuation in strings) unmodified.
if v == scanContinue {
dst = append(dst, c)
continue
}
// Add spacing around real punctuation.
switch c {
case '{', '[':
// delay indent so that empty object and array are formatted as {} and [].
needIndent = true
dst = append(dst, c)
case ',':
dst = append(dst, c)
dst = appendNewline(dst, prefix, indent, depth)
case ':':
dst = append(dst, c, ' ')
case '}', ']':
if needIndent {
// suppress indent in empty object/array
needIndent = false
} else {
depth--
dst = appendNewline(dst, prefix, indent, depth)
}
dst = append(dst, c)
default:
dst = append(dst, c)
}
}
if scan.eof() == scanError {
return dst[:origLen], scan.err
}
return dst, nil
}
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