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Merge pull request #3305 from knl/interpret-u-escapes-in-JSON-strings

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Add support for unicode escape sequences in fromJSON
This commit is contained in:
Eelco Dolstra 2020-01-07 01:04:16 +01:00 committed by GitHub
commit 04bbfa692f
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3 changed files with 90 additions and 3 deletions
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89
src/libexpr/json-to-value.cc
View file

@ -11,6 +11,87 @@ static void skipWhitespace(const char * & s)
}
/*
Parse an unicode escape sequence (4 hex characters following \u) in JSON string
*/
static string parseUnicodeEscapeSequence(const char * & s)
{
int codepoint = 0;
const auto factors = { 12u, 8u, 4u, 0u };
for (const auto factor : factors)
{
if (!*s) throw JSONParseError("got end-of-string in JSON string while parsing \\u sequence");
if (*s >= '0' and *s <= '9') {
codepoint += static_cast<int>((static_cast<unsigned int>(*s) - 0x30u) << factor);
} else if (*s >= 'A' and *s <= 'F') {
codepoint += static_cast<int>((static_cast<unsigned int>(*s) - 0x37u) << factor);
} else if (*s >= 'a' and *s <= 'f') {
codepoint += static_cast<int>((static_cast<unsigned int>(*s) - 0x57u) << factor);
} else {
throw JSONParseError(format("illegal character '%1%' in \\u escape sequence.") % *s);
}
s++;
}
if ((codepoint > 0xd7ff && codepoint < 0xe000) || codepoint > 0x10ffff) {
throw JSONParseError("Unicode escape sequence is not a Unicode scalar value");
}
// taken from cpptoml.h
std::string result;
// See Table 3-6 of the Unicode standard
if (codepoint <= 0x7f)
{
// 1-byte codepoints: 00000000 0xxxxxxx
// repr: 0xxxxxxx
result += static_cast<char>(codepoint & 0x7f);
}
else if (codepoint <= 0x7ff)
{
// 2-byte codepoints: 00000yyy yyxxxxxx
// repr: 110yyyyy 10xxxxxx
//
// 0x1f = 00011111
// 0xc0 = 11000000
//
result += static_cast<char>(0xc0 | ((codepoint >> 6) & 0x1f));
//
// 0x80 = 10000000
// 0x3f = 00111111
//
result += static_cast<char>(0x80 | (codepoint & 0x3f));
}
else if (codepoint <= 0xffff)
{
// 3-byte codepoints: zzzzyyyy yyxxxxxx
// repr: 1110zzzz 10yyyyyy 10xxxxxx
//
// 0xe0 = 11100000
// 0x0f = 00001111
//
result += static_cast<char>(0xe0 | ((codepoint >> 12) & 0x0f));
result += static_cast<char>(0x80 | ((codepoint >> 6) & 0x1f));
result += static_cast<char>(0x80 | (codepoint & 0x3f));
}
else
{
// 4-byte codepoints: 000uuuuu zzzzyyyy yyxxxxxx
// repr: 11110uuu 10uuzzzz 10yyyyyy 10xxxxxx
//
// 0xf0 = 11110000
// 0x07 = 00000111
//
result += static_cast<char>(0xf0 | ((codepoint >> 18) & 0x07));
result += static_cast<char>(0x80 | ((codepoint >> 12) & 0x3f));
result += static_cast<char>(0x80 | ((codepoint >> 6) & 0x3f));
result += static_cast<char>(0x80 | (codepoint & 0x3f));
}
return result;
}
static string parseJSONString(const char * & s)
{
string res;
@ -22,14 +103,16 @@ static string parseJSONString(const char * & s)
if (*s == '"') res += '"';
else if (*s == '\\') res += '\\';
else if (*s == '/') res += '/';
else if (*s == '/') res += '/';
else if (*s == 'b') res += '\b';
else if (*s == 'f') res += '\f';
else if (*s == 'n') res += '\n';
else if (*s == 'r') res += '\r';
else if (*s == 't') res += '\t';
else if (*s == 'u') throw JSONParseError("\\u characters in JSON strings are currently not supported");
else throw JSONParseError("invalid escaped character in JSON string");
else if (*s == 'u') {
res += parseUnicodeEscapeSequence(++s);
// to neuter the outside s++
s--;
} else throw JSONParseError("invalid escaped character in JSON string");
s++;
} else
res += *s++;

1
tests/lang/eval-okay-fromjson-escapes.exp Normal file
View file

@ -0,0 +1 @@
"quote \" reverse solidus \\ solidus / backspace  formfeed newline \n carriage return \r horizontal tab \t 1 char unicode encoded backspace  1 char unicode encoded e with accent é 2 char unicode encoded s with caron š 3 char unicode encoded rightwards arrow →"

3
tests/lang/eval-okay-fromjson-escapes.nix Normal file
View file

@ -0,0 +1,3 @@
# This string contains all supported escapes in a JSON string, per json.org
# \b and \f are not supported by Nix
builtins.fromJSON ''"quote \" reverse solidus \\ solidus \/ backspace \b formfeed \f newline \n carriage return \r horizontal tab \t 1 char unicode encoded backspace \u0008 1 char unicode encoded e with accent \u00e9 2 char unicode encoded s with caron \u0161 3 char unicode encoded rightwards arrow \u2192"''