Add more SimpleAtod / SimpleAtof test coverage

PiperOrigin-RevId: 465451170
Change-Id: I5fd161b1ef156d60d7f9a6ecf493bcf802d581e8
diff --git a/absl/strings/BUILD.bazel b/absl/strings/BUILD.bazel
index 3f51252..ba7ae83 100644
--- a/absl/strings/BUILD.bazel
+++ b/absl/strings/BUILD.bazel
@@ -1279,3 +1279,18 @@
         "@com_google_googletest//:gtest_main",
     ],
 )
+
+cc_binary(
+    name = "atod_manual_test",
+    testonly = 1,
+    srcs = ["atod_manual_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        ":str_format",
+        ":strings",
+        "//absl/base",
+        "//absl/types:optional",
+    ],
+)
diff --git a/absl/strings/atod_manual_test.cc b/absl/strings/atod_manual_test.cc
new file mode 100644
index 0000000..6cf28b0
--- /dev/null
+++ b/absl/strings/atod_manual_test.cc
@@ -0,0 +1,193 @@
+// Copyright 2022 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This program tests the absl::SimpleAtod and absl::SimpleAtof functions. Run
+// it as "atod_manual_test pnftd/data/*.txt" where the pnftd directory is a
+// local checkout of the https://github.com/nigeltao/parse-number-fxx-test-data
+// repository. The test suite lives in a separate repository because its more
+// than 5 million test cases weigh over several hundred megabytes and because
+// the test cases are also useful to other software projects, not just Abseil.
+// Its data/*.txt files contain one test case per line, like:
+//
+// 3C00 3F800000 3FF0000000000000 1
+// 3D00 3FA00000 3FF4000000000000 1.25
+// 3D9A 3FB33333 3FF6666666666666 1.4
+// 57B7 42F6E979 405EDD2F1A9FBE77 123.456
+// 622A 44454000 4088A80000000000 789
+// 7C00 7F800000 7FF0000000000000 123.456e789
+//
+// For each line (and using 0-based column indexes), columns [5..13] and
+// [14..30] contain the 32-bit float and 64-bit double result of parsing
+// columns [31..].
+//
+// For example, parsing "1.4" as a float gives the bits 0x3FB33333.
+//
+// In this 6-line example, the final line's float and double values are all
+// infinity. The largest finite float and double values are approximately
+// 3.40e+38 and 1.80e+308.
+
+#include <cstdint>
+#include <cstdio>
+#include <string>
+
+#include "absl/base/casts.h"
+#include "absl/strings/numbers.h"
+#include "absl/strings/str_format.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+
+static constexpr uint8_t kUnhex[256] = {
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7,  // '0' ..= '7'
+    0x8, 0x9, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  // '8' ..= '9'
+
+    0x0, 0xA, 0xB, 0xC, 0xD, 0xE, 0xF, 0x0,  // 'A' ..= 'F'
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,  //
+};
+
+static absl::optional<std::string> ReadFileToString(const char* filename) {
+  FILE* f = fopen(filename, "rb");
+  if (!f) {
+    return absl::nullopt;
+  }
+  fseek(f, 0, SEEK_END);
+  size_t size = ftell(f);
+  fseek(f, 0, SEEK_SET);
+  std::string s(size, '\x00');
+  size_t n = fread(&s[0], 1, size, f);
+  fclose(f);
+  if (n != size) {
+    return absl::nullopt;
+  }
+  return s;
+}
+
+static bool ProcessOneTestFile(const char* filename) {
+  absl::optional<std::string> contents = ReadFileToString(filename);
+  if (!contents) {
+    absl::FPrintF(stderr, "Invalid file: %s\n", filename);
+    return false;
+  }
+
+  int num_cases = 0;
+  for (absl::string_view v(*contents); !v.empty();) {
+    size_t new_line = v.find('\n');
+    if ((new_line == absl::string_view::npos) || (new_line < 32)) {
+      break;
+    }
+    absl::string_view input = v.substr(31, new_line - 31);
+
+    // Test absl::SimpleAtof.
+    {
+      float f;
+      if (!absl::SimpleAtof(input, &f)) {
+        absl::FPrintF(stderr, "Could not parse \"%s\" in %s\n", input,
+                      filename);
+        return false;
+      }
+      uint32_t have32 = absl::bit_cast<uint32_t>(f);
+
+      uint32_t want32 = 0;
+      for (int i = 0; i < 8; i++) {
+        want32 = (want32 << 4) | kUnhex[static_cast<unsigned char>(v[5 + i])];
+      }
+
+      if (have32 != want32) {
+        absl::FPrintF(stderr,
+                      "absl::SimpleAtof failed parsing \"%s\" in %s\n  have  "
+                      "%08X\n  want  %08X\n",
+                      input, filename, have32, want32);
+        return false;
+      }
+    }
+
+    // Test absl::SimpleAtod.
+    {
+      double d;
+      if (!absl::SimpleAtod(input, &d)) {
+        absl::FPrintF(stderr, "Could not parse \"%s\" in %s\n", input,
+                      filename);
+        return false;
+      }
+      uint64_t have64 = absl::bit_cast<uint64_t>(d);
+
+      uint64_t want64 = 0;
+      for (int i = 0; i < 16; i++) {
+        want64 = (want64 << 4) | kUnhex[static_cast<unsigned char>(v[14 + i])];
+      }
+
+      if (have64 != want64) {
+        absl::FPrintF(stderr,
+                      "absl::SimpleAtod failed parsing \"%s\" in %s\n  have  "
+                      "%016X\n  want  %016X\n",
+                      input, filename, have64, want64);
+        return false;
+      }
+    }
+
+    num_cases++;
+    v = v.substr(new_line + 1);
+  }
+  printf("%8d OK in %s\n", num_cases, filename);
+  return true;
+}
+
+int main(int argc, char** argv) {
+  if (argc < 2) {
+    absl::FPrintF(
+        stderr,
+        "Usage: %s pnftd/data/*.txt\nwhere the pnftd directory is a local "
+        "checkout of "
+        "the\nhttps://github.com/nigeltao/parse-number-fxx-test-data "
+        "repository.\n",
+        argv[0]);
+    return 1;
+  }
+
+  for (int i = 1; i < argc; i++) {
+    if (!ProcessOneTestFile(argv[i])) {
+      return 1;
+    }
+  }
+  return 0;
+}
diff --git a/absl/strings/numbers_test.cc b/absl/strings/numbers_test.cc
index 498c210..04e4bd2 100644
--- a/absl/strings/numbers_test.cc
+++ b/absl/strings/numbers_test.cc
@@ -389,8 +389,63 @@
 
 TEST(NumbersTest, Atod) {
   double d;
-  EXPECT_TRUE(absl::SimpleAtod("nan", &d));
+
+  // NaN can be spelled in multiple ways.
+  EXPECT_TRUE(absl::SimpleAtod("NaN", &d));
   EXPECT_TRUE(std::isnan(d));
+  EXPECT_TRUE(absl::SimpleAtod("nAN", &d));
+  EXPECT_TRUE(std::isnan(d));
+  EXPECT_TRUE(absl::SimpleAtod("-nan", &d));
+  EXPECT_TRUE(std::isnan(d));
+
+  // Likewise for Infinity.
+  EXPECT_TRUE(absl::SimpleAtod("inf", &d));
+  EXPECT_TRUE(std::isinf(d) && (d > 0));
+  EXPECT_TRUE(absl::SimpleAtod("+Infinity", &d));
+  EXPECT_TRUE(std::isinf(d) && (d > 0));
+  EXPECT_TRUE(absl::SimpleAtod("-INF", &d));
+  EXPECT_TRUE(std::isinf(d) && (d < 0));
+
+  // Leading and/or trailing whitespace is OK.
+  EXPECT_TRUE(absl::SimpleAtod("  \t\r\n  2.718", &d));
+  EXPECT_EQ(d, 2.718);
+  EXPECT_TRUE(absl::SimpleAtod("  3.141  ", &d));
+  EXPECT_EQ(d, 3.141);
+
+  // Leading or trailing not-whitespace is not OK.
+  EXPECT_FALSE(absl::SimpleAtod("n 0", &d));
+  EXPECT_FALSE(absl::SimpleAtod("0n ", &d));
+
+  // Multiple leading 0s are OK.
+  EXPECT_TRUE(absl::SimpleAtod("000123", &d));
+  EXPECT_EQ(d, 123);
+  EXPECT_TRUE(absl::SimpleAtod("000.456", &d));
+  EXPECT_EQ(d, 0.456);
+
+  // An absent leading 0 (for a fraction < 1) is OK.
+  EXPECT_TRUE(absl::SimpleAtod(".5", &d));
+  EXPECT_EQ(d, 0.5);
+  EXPECT_TRUE(absl::SimpleAtod("-.707", &d));
+  EXPECT_EQ(d, -0.707);
+
+  // Unary + is OK.
+  EXPECT_TRUE(absl::SimpleAtod("+6.0221408e+23", &d));
+  EXPECT_EQ(d, 6.0221408e+23);
+
+  // Underscores are not OK.
+  EXPECT_FALSE(absl::SimpleAtod("123_456", &d));
+
+  // The decimal separator must be '.' and is never ','.
+  EXPECT_TRUE(absl::SimpleAtod("8.9", &d));
+  EXPECT_FALSE(absl::SimpleAtod("8,9", &d));
+
+  // Some parsing algorithms don't always round correctly (but absl::SimpleAtod
+  // should). This test case comes from
+  // https://github.com/serde-rs/json/issues/707
+  //
+  // See also atod_manual_test.cc for running many more test cases.
+  EXPECT_TRUE(absl::SimpleAtod("122.416294033786585", &d));
+  EXPECT_EQ(d, 122.416294033786585);
 }
 
 TEST(NumbersTest, Prefixes) {