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[skjson] Unescape strings
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Bug: skia:
Change-Id: Ie40f498c87cb57ee59c9bea41b1ff3d81a9b5858
Reviewed-on: https://skia-review.googlesource.com/c/167240
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
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@fmalita
fmalita authored and Skia Commit-Bot committed Nov 5, 2018
1 parent cb42b91 commit 20fda9c
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Showing 2 changed files with 110 additions and 6 deletions.
88 changes: 82 additions & 6 deletions src/utils/SkJSON.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -8,8 +8,10 @@
#include "SkJSON.h"

#include "SkMalloc.h"
#include "SkParse.h"
#include "SkStream.h"
#include "SkString.h"
#include "SkUTF.h"

#include <cmath>
#include <tuple>
Expand Down Expand Up @@ -226,7 +228,7 @@ namespace {

// bit 0 (0x01) - plain ASCII string character
// bit 1 (0x02) - whitespace
// bit 2 (0x04) - string terminator (" \0 [control chars] **AND } ]** <- see matchString notes)
// bit 2 (0x04) - string terminator (" \\ \0 [control chars] **AND } ]** <- see matchString notes)
// bit 3 (0x08) - 0-9
// bit 4 (0x10) - 0-9 e E .
// bit 5 (0x20) - scope terminator (} ])
Expand All @@ -237,7 +239,7 @@ static constexpr uint8_t g_token_flags[256] = {
3, 1, 4, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0x11,1, // 2
0x19,0x19,0x19,0x19,0x19,0x19,0x19,0x19, 0x19,0x19, 1, 1, 1, 1, 1, 1, // 3
1, 1, 1, 1, 1, 0x11,1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 4
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0,0x25, 1, 1, // 5
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 4,0x25, 1, 1, // 5
1, 1, 1, 1, 1, 0x11,1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 6
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,0x25, 1, 1, // 7

Expand Down Expand Up @@ -286,6 +288,7 @@ class DOMParser {
explicit DOMParser(SkArenaAlloc& alloc)
: fAlloc(alloc) {
fValueStack.reserve(kValueStackReserve);
fUnescapeBuffer.reserve(kUnescapeBufferReserve);
}

const Value parse(const char* p, size_t size) {
Expand Down Expand Up @@ -460,6 +463,10 @@ class DOMParser {
static constexpr size_t kValueStackReserve = 256;
std::vector<Value> fValueStack;

// String unescape buffer.
static constexpr size_t kUnescapeBufferReserve = 512;
std::vector<char> fUnescapeBuffer;

// Tracks the current object/array scope, as an index into fStack:
//
// - for objects: fScopeIndex = (index of first value in scope)
Expand Down Expand Up @@ -626,28 +633,97 @@ class DOMParser {
return this->error(nullptr, p, "invalid token");
}

const std::vector<char>* unescapeString(const char* begin, const char* end) {
fUnescapeBuffer.clear();

for (const auto* p = begin; p != end; ++p) {
if (*p != '\\') {
fUnescapeBuffer.push_back(*p);
continue;
}

if (++p == end) {
return nullptr;
}

switch (*p) {
case '"': fUnescapeBuffer.push_back( '"'); break;
case '\\': fUnescapeBuffer.push_back('\\'); break;
case '/': fUnescapeBuffer.push_back( '/'); break;
case 'b': fUnescapeBuffer.push_back('\b'); break;
case 'f': fUnescapeBuffer.push_back('\f'); break;
case 'n': fUnescapeBuffer.push_back('\n'); break;
case 'r': fUnescapeBuffer.push_back('\r'); break;
case 't': fUnescapeBuffer.push_back('\t'); break;
case 'u': {
if (p + 4 >= end) {
return nullptr;
}

uint32_t hexed;
const char hex_str[] = {p[1], p[2], p[3], p[4], '\0'};
const auto* eos = SkParse::FindHex(hex_str, &hexed);
if (!eos || *eos) {
return nullptr;
}

char utf8[SkUTF::kMaxBytesInUTF8Sequence];
const auto utf8_len = SkUTF::ToUTF8(SkTo<SkUnichar>(hexed), utf8);
fUnescapeBuffer.insert(fUnescapeBuffer.end(), utf8, utf8 + utf8_len);
p += 4;
} break;
default: return nullptr;
}
}

return &fUnescapeBuffer;
}

template <typename MatchFunc>
const char* matchString(const char* p, const char* p_stop, MatchFunc&& func) {
SkASSERT(*p == '"');
const auto* s_begin = p + 1;

// TODO: unescape
bool requires_unescape = false;

do {
// Consume string chars.
// This is the fast path, and hopefully we only hit it once then quick-exit below.
for (p = p + 1; !is_eostring(*p); ++p);

if (*p == '"') {
// Valid string found.
func(s_begin, p - s_begin, p_stop);
if (!requires_unescape) {
func(s_begin, p - s_begin, p_stop);
} else {
// Slow unescape. We could avoid this extra copy with some effort,
// but in practice escaped strings should be rare.
const auto* buf = this->unescapeString(s_begin, p);
if (!buf) {
break;
}

func(buf->data(), buf->size(), buf->data() + buf->capacity());
}
return p + 1;
}

if (*p == '\\') {
requires_unescape = true;
++p;
continue;
}

// End-of-scope chars are special: we use them to tag the end of the input.
// Thus they cannot be consumed indiscriminately -- we need to check if we hit the
// end of the input. To that effect, we treat them as string terminators above,
// then we catch them here.
} while (is_eoscope(*p) && (p != p_stop)); // Safe scope terminator char, keep going.
if (is_eoscope(*p)) {
continue;
}

// Invalid/unexpected char.
break;
} while (p != p_stop);

// Premature end-of-input, or illegal string char.
return this->error(nullptr, s_begin - 1, "invalid string");
Expand Down
28 changes: 28 additions & 0 deletions tests/JSONTest.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,14 @@ DEF_TEST(JSON_Parse, reporter) {
{ "{ \"k\" : null , }" , nullptr },
{ "{ \"k\" : null \"k\" : 1 }", nullptr },

{R"zzz(["\)zzz" , nullptr},
{R"zzz(["\])zzz" , nullptr},
{R"zzz(["\"])zzz" , nullptr},
{R"zzz(["\z"])zzz" , nullptr},
{R"zzz(["\u"])zzz" , nullptr},
{R"zzz(["\u0"])zzz" , nullptr},
{R"zzz(["\u00"])zzz" , nullptr},
{R"zzz(["\u000"])zzz", nullptr},

{ "[]" , "[]" },
{ " \n\r\t [ \n\r\t ] \n\r\t " , "[]" },
Expand Down Expand Up @@ -100,6 +108,26 @@ DEF_TEST(JSON_Parse, reporter) {
}",
"{\"k1\":null,\"k2\":0,\"k3\":[true,"
"{\"kk1\":\"foo\",\"kk2\":\"bar\",\"kk3\":1.28,\"kk4\":[42]},\"boo\",null]}" },

{R"zzz(["\""])zzz" , "[\"\"\"]"},
{R"zzz(["\\"])zzz" , "[\"\\\"]"},
{R"zzz(["\/"])zzz" , "[\"/\"]" },
{R"zzz(["\b"])zzz" , "[\"\b\"]"},
{R"zzz(["\f"])zzz" , "[\"\f\"]"},
{R"zzz(["\n"])zzz" , "[\"\n\"]"},
{R"zzz(["\r"])zzz" , "[\"\r\"]"},
{R"zzz(["\t"])zzz" , "[\"\t\"]"},
{R"zzz(["\u1234"])zzz", "[\"\u1234\"]"},

{R"zzz(["foo\"bar"])zzz" , "[\"foo\"bar\"]"},
{R"zzz(["foo\\bar"])zzz" , "[\"foo\\bar\"]"},
{R"zzz(["foo\/bar"])zzz" , "[\"foo/bar\"]" },
{R"zzz(["foo\bbar"])zzz" , "[\"foo\bbar\"]"},
{R"zzz(["foo\fbar"])zzz" , "[\"foo\fbar\"]"},
{R"zzz(["foo\nbar"])zzz" , "[\"foo\nbar\"]"},
{R"zzz(["foo\rbar"])zzz" , "[\"foo\rbar\"]"},
{R"zzz(["foo\tbar"])zzz" , "[\"foo\tbar\"]"},
{R"zzz(["foo\u1234bar"])zzz", "[\"foo\u1234bar\"]"},
};

for (const auto& tst : g_tests) {
Expand Down

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