1 files changed, 149 insertions, 0 deletions
diff --git a/third_party/nix/src/libexpr/json-to-value.cc b/third_party/nix/src/libexpr/json-to-value.cc
new file mode 100644
index 000000000000..8bae986f97fc
--- /dev/null
+++ b/third_party/nix/src/libexpr/json-to-value.cc
@@ -0,0 +1,149 @@
+#include "json-to-value.hh"
+
+#include <cstring>
+
+namespace nix {
+
+
+static void skipWhitespace(const char * & s)
+{
+    while (*s == ' ' || *s == '\t' || *s == '\n' || *s == '\r') s++;
+}
+
+
+static string parseJSONString(const char * & s)
+{
+    string res;
+    if (*s++ != '"') throw JSONParseError("expected JSON string");
+    while (*s != '"') {
+        if (!*s) throw JSONParseError("got end-of-string in JSON string");
+        if (*s == '\\') {
+            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");
+            s++;
+        } else
+            res += *s++;
+    }
+    s++;
+    return res;
+}
+
+
+static void parseJSON(EvalState & state, const char * & s, Value & v)
+{
+    skipWhitespace(s);
+
+    if (!*s) throw JSONParseError("expected JSON value");
+
+    if (*s == '[') {
+        s++;
+        ValueVector values;
+        values.reserve(128);
+        skipWhitespace(s);
+        while (1) {
+            if (values.empty() && *s == ']') break;
+            Value * v2 = state.allocValue();
+            parseJSON(state, s, *v2);
+            values.push_back(v2);
+            skipWhitespace(s);
+            if (*s == ']') break;
+            if (*s != ',') throw JSONParseError("expected ',' or ']' after JSON array element");
+            s++;
+        }
+        s++;
+        state.mkList(v, values.size());
+        for (size_t n = 0; n < values.size(); ++n)
+            v.listElems()[n] = values[n];
+    }
+
+    else if (*s == '{') {
+        s++;
+        ValueMap attrs;
+        while (1) {
+            skipWhitespace(s);
+            if (attrs.empty() && *s == '}') break;
+            string name = parseJSONString(s);
+            skipWhitespace(s);
+            if (*s != ':') throw JSONParseError("expected ':' in JSON object");
+            s++;
+            Value * v2 = state.allocValue();
+            parseJSON(state, s, *v2);
+            attrs[state.symbols.create(name)] = v2;
+            skipWhitespace(s);
+            if (*s == '}') break;
+            if (*s != ',') throw JSONParseError("expected ',' or '}' after JSON member");
+            s++;
+        }
+        state.mkAttrs(v, attrs.size());
+        for (auto & i : attrs)
+            v.attrs->push_back(Attr(i.first, i.second));
+        v.attrs->sort();
+        s++;
+    }
+
+    else if (*s == '"') {
+        mkString(v, parseJSONString(s));
+    }
+
+    else if (isdigit(*s) || *s == '-' || *s == '.' ) {
+        // Buffer into a string first, then use built-in C++ conversions
+        std::string tmp_number;
+        ValueType number_type = tInt;
+
+        while (isdigit(*s) || *s == '-' || *s == '.' || *s == 'e' || *s == 'E') {
+            if (*s == '.' || *s == 'e' || *s == 'E')
+                number_type = tFloat;
+            tmp_number += *s++;
+        }
+
+        try {
+            if (number_type == tFloat)
+                mkFloat(v, stod(tmp_number));
+            else
+                mkInt(v, stol(tmp_number));
+        } catch (std::invalid_argument & e) {
+            throw JSONParseError("invalid JSON number");
+        } catch (std::out_of_range & e) {
+            throw JSONParseError("out-of-range JSON number");
+        }
+    }
+
+    else if (strncmp(s, "true", 4) == 0) {
+        s += 4;
+        mkBool(v, true);
+    }
+
+    else if (strncmp(s, "false", 5) == 0) {
+        s += 5;
+        mkBool(v, false);
+    }
+
+    else if (strncmp(s, "null", 4) == 0) {
+        s += 4;
+        mkNull(v);
+    }
+
+    else throw JSONParseError("unrecognised JSON value");
+}
+
+
+void parseJSON(EvalState & state, const string & s_, Value & v)
+{
+    const char * s = s_.c_str();
+    parseJSON(state, s, v);
+    skipWhitespace(s);
+    if (*s) throw JSONParseError(format("expected end-of-string while parsing JSON value: %1%") % s);
+}
+
+
+}