Add a simple Atoi64.

This will be useful in parsing numeric HTTP params.

src/string-test.cc

@@ -112,6 +112,16 @@ TEST(HumanizeTest, Simple) {
   EXPECT_EQ("1000.0 Ebps", HumanizeWithDecimalPrefix(1e21, "bps"));
 }
 
+TEST(AtoiTest, Simple) {
+  int64_t out;
+  EXPECT_TRUE(Atoi64("1234", 10, &out));
+  EXPECT_EQ(1234, out);
+  EXPECT_FALSE(Atoi64(nullptr, 10, &out));
+  EXPECT_FALSE(Atoi64("", 10, &out));
+  EXPECT_FALSE(Atoi64("asdf", 10, &out));
+  EXPECT_FALSE(Atoi64("1234asdf", 10, &out));
+}
+
 }  // namespace
 }  // namespace moonfire_nvr
 

src/string.cc

@@ -148,9 +148,17 @@ std::string HumanizeWithBinaryPrefix(float n, re2::StringPiece suffix) {
 bool strto64(const char *str, int base, const char **endptr, int64_t *value) {
   static_assert(sizeof(int64_t) == sizeof(long long int),
                 "unknown memory model");
+  if (str == nullptr) {
+    return false;
+  }
   errno = 0;
   *value = ::strtoll(str, const_cast<char **>(endptr), base);
   return *endptr != str && errno == 0;
 }
 
+bool Atoi64(const char *str, int base, int64_t *value) {
+  const char *endptr;
+  return strto64(str, base, &endptr, value) && *endptr == '\0';
+}
+
 }  // namespace moonfire_nvr

src/string.h

@@ -127,10 +127,13 @@ std::string ToHex(re2::StringPiece in, bool pad = false);
 std::string HumanizeWithDecimalPrefix(float n, re2::StringPiece suffix);
 std::string HumanizeWithBinaryPrefix(float n, re2::StringPiece suffix);
 
-// Wrapper around ::strtol that returns true iff valid and corrects
-// constness.
+// Wrapper around ::strtoll that returns true iff valid and corrects
+// constness. Returns false if |str| is null.
 bool strto64(const char *str, int base, const char **endptr, int64_t *value);
 
+// Simpler form that expects the entire string to be a single integer.
+bool Atoi64(const char *str, int base, int64_t *value);
+
 }  // namespace moonfire_nvr
 
 #endif  // MOONFIRE_NVR_STRING_H