codekingpro/portable-devtools

1// Copyright 2010 The Go Authors. All rights reserved.2// Use of this source code is governed by a BSD-style3// license that can be found in the LICENSE file.4 5//go:build !goexperiment.jsonv26 7package json8 9import "bytes"10 11// HTMLEscape appends to dst the JSON-encoded src with <, >, &, U+2028 and U+202912// characters inside string literals changed to \u003c, \u003e, \u0026, \u2028, \u202913// so that the JSON will be safe to embed inside HTML <script> tags.14// For historical reasons, web browsers don't honor standard HTML15// escaping within <script> tags, so an alternative JSON encoding must be used.16func HTMLEscape(dst *bytes.Buffer, src []byte) {17	dst.Grow(len(src))18	dst.Write(appendHTMLEscape(dst.AvailableBuffer(), src))19}20 21func appendHTMLEscape(dst, src []byte) []byte {22	// The characters can only appear in string literals,23	// so just scan the string one byte at a time.24	start := 025	for i, c := range src {26		if c == '<' || c == '>' || c == '&' {27			dst = append(dst, src[start:i]...)28			dst = append(dst, '\\', 'u', '0', '0', hex[c>>4], hex[c&0xF])29			start = i + 130		}31		// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).32		if c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {33			dst = append(dst, src[start:i]...)34			dst = append(dst, '\\', 'u', '2', '0', '2', hex[src[i+2]&0xF])35			start = i + len("\u2029")36		}37	}38	return append(dst, src[start:]...)39}40 41// Compact appends to dst the JSON-encoded src with42// insignificant space characters elided.43func Compact(dst *bytes.Buffer, src []byte) error {44	dst.Grow(len(src))45	b := dst.AvailableBuffer()46	b, err := appendCompact(b, src, false)47	dst.Write(b)48	return err49}50 51func appendCompact(dst, src []byte, escape bool) ([]byte, error) {52	origLen := len(dst)53	scan := newScanner()54	defer freeScanner(scan)55	start := 056	for i, c := range src {57		if escape && (c == '<' || c == '>' || c == '&') {58			if start < i {59				dst = append(dst, src[start:i]...)60			}61			dst = append(dst, '\\', 'u', '0', '0', hex[c>>4], hex[c&0xF])62			start = i + 163		}64		// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).65		if escape && c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {66			if start < i {67				dst = append(dst, src[start:i]...)68			}69			dst = append(dst, '\\', 'u', '2', '0', '2', hex[src[i+2]&0xF])70			start = i + 371		}72		v := scan.step(scan, c)73		if v >= scanSkipSpace {74			if v == scanError {75				break76			}77			if start < i {78				dst = append(dst, src[start:i]...)79			}80			start = i + 181		}82	}83	if scan.eof() == scanError {84		return dst[:origLen], scan.err85	}86	if start < len(src) {87		dst = append(dst, src[start:]...)88	}89	return dst, nil90}91 92func appendNewline(dst []byte, prefix, indent string, depth int) []byte {93	dst = append(dst, '\n')94	dst = append(dst, prefix...)95	for i := 0; i < depth; i++ {96		dst = append(dst, indent...)97	}98	return dst99}100 101// indentGrowthFactor specifies the growth factor of indenting JSON input.102// Empirically, the growth factor was measured to be between 1.4x to 1.8x103// for some set of compacted JSON with the indent being a single tab.104// Specify a growth factor slightly larger than what is observed105// to reduce probability of allocation in appendIndent.106// A factor no higher than 2 ensures that wasted space never exceeds 50%.107const indentGrowthFactor = 2108 109// Indent appends to dst an indented form of the JSON-encoded src.110// Each element in a JSON object or array begins on a new,111// indented line beginning with prefix followed by one or more112// copies of indent according to the indentation nesting.113// The data appended to dst does not begin with the prefix nor114// any indentation, to make it easier to embed inside other formatted JSON data.115// Although leading space characters (space, tab, carriage return, newline)116// at the beginning of src are dropped, trailing space characters117// at the end of src are preserved and copied to dst.118// For example, if src has no trailing spaces, neither will dst;119// if src ends in a trailing newline, so will dst.120func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error {121	dst.Grow(indentGrowthFactor * len(src))122	b := dst.AvailableBuffer()123	b, err := appendIndent(b, src, prefix, indent)124	dst.Write(b)125	return err126}127 128func appendIndent(dst, src []byte, prefix, indent string) ([]byte, error) {129	origLen := len(dst)130	scan := newScanner()131	defer freeScanner(scan)132	needIndent := false133	depth := 0134	for _, c := range src {135		scan.bytes++136		v := scan.step(scan, c)137		if v == scanSkipSpace {138			continue139		}140		if v == scanError {141			break142		}143		if needIndent && v != scanEndObject && v != scanEndArray {144			needIndent = false145			depth++146			dst = appendNewline(dst, prefix, indent, depth)147		}148 149		// Emit semantically uninteresting bytes150		// (in particular, punctuation in strings) unmodified.151		if v == scanContinue {152			dst = append(dst, c)153			continue154		}155 156		// Add spacing around real punctuation.157		switch c {158		case '{', '[':159			// delay indent so that empty object and array are formatted as {} and [].160			needIndent = true161			dst = append(dst, c)162		case ',':163			dst = append(dst, c)164			dst = appendNewline(dst, prefix, indent, depth)165		case ':':166			dst = append(dst, c, ' ')167		case '}', ']':168			if needIndent {169				// suppress indent in empty object/array170				needIndent = false171			} else {172				depth--173				dst = appendNewline(dst, prefix, indent, depth)174			}175			dst = append(dst, c)176		default:177			dst = append(dst, c)178		}179	}180	if scan.eof() == scanError {181		return dst[:origLen], scan.err182	}183	return dst, nil184}185