1 files changed, 185 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..d46e6f268e9f
--- /dev/null
+++ b/third_party/nix/src/libexpr/json-to-value.cc
@@ -0,0 +1,185 @@
+#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 std::string parseJSONString(const char*& s) {
+  std::string res;
+  if (*s++ != '"') {
+    throw JSONParseError("expected JSON string");
+  }
+  while (*s != '"') {
+    if (*s == 0) {
+      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 == 0) {
+    throw JSONParseError("expected JSON value");
+  }
+
+  if (*s == '[') {
+    s++;
+    ValueVector values;
+    values.reserve(128);
+    skipWhitespace(s);
+    while (true) {
+      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 (true) {
+      skipWhitespace(s);
+      if (attrs.empty() && *s == '}') {
+        break;
+      }
+      std::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));
+    }
+    s++;
+  }
+
+  else if (*s == '"') {
+    mkString(v, parseJSONString(s));
+  }
+
+  else if ((isdigit(*s) != 0) || *s == '-' || *s == '.') {
+    // Buffer into a std::string first, then use built-in C++ conversions
+    std::string tmp_number;
+    ValueType number_type = tInt;
+
+    while ((isdigit(*s) != 0) || *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 std::string& s_, Value& v) {
+  const char* s = s_.c_str();
+  parseJSON(state, s, v);
+  skipWhitespace(s);
+  if (*s != 0) {
+    throw JSONParseError(
+        format("expected end-of-string while parsing JSON value: %1%") % s);
+  }
+}
+
+}  // namespace nix