diff options
Diffstat (limited to 'src/libutil/json.cc')
| -rw-r--r-- | src/libutil/json.cc | 42 |
1 files changed, 32 insertions, 10 deletions
diff --git a/src/libutil/json.cc b/src/libutil/json.cc index 01331947e..3a981376f 100644 --- a/src/libutil/json.cc +++ b/src/libutil/json.cc @@ -7,16 +7,38 @@ namespace nix { void toJSON(std::ostream & str, const char * start, const char * end) { - str << '"'; - for (auto i = start; i != end; i++) - if (*i == '\"' || *i == '\\') str << '\\' << *i; - else if (*i == '\n') str << "\\n"; - else if (*i == '\r') str << "\\r"; - else if (*i == '\t') str << "\\t"; - else if (*i >= 0 && *i < 32) - str << "\\u" << std::setfill('0') << std::setw(4) << std::hex << (uint16_t) *i << std::dec; - else str << *i; - str << '"'; + constexpr size_t BUF_SIZE = 4096; + char buf[BUF_SIZE + 7]; // BUF_SIZE + largest single sequence of puts + size_t bufPos = 0; + + const auto flush = [&] { + str.write(buf, bufPos); + bufPos = 0; + }; + const auto put = [&] (char c) { + buf[bufPos++] = c; + }; + + put('"'); + for (auto i = start; i != end; i++) { + if (bufPos >= BUF_SIZE) flush(); + if (*i == '\"' || *i == '\\') { put('\\'); put(*i); } + else if (*i == '\n') { put('\\'); put('n'); } + else if (*i == '\r') { put('\\'); put('r'); } + else if (*i == '\t') { put('\\'); put('t'); } + else if (*i >= 0 && *i < 32) { + const char hex[17] = "0123456789abcdef"; + put('\\'); + put('u'); + put(hex[(uint16_t(*i) >> 12) & 0xf]); + put(hex[(uint16_t(*i) >> 8) & 0xf]); + put(hex[(uint16_t(*i) >> 4) & 0xf]); + put(hex[(uint16_t(*i) >> 0) & 0xf]); + } + else put(*i); + } + put('"'); + flush(); } void toJSON(std::ostream & str, const char * s) |