SkPDF: fix scalar serialization

tests/PDFPrimitivesTest.cpp

Index: tests/PDFPrimitivesTest.cpp
diff --git a/tests/PDFPrimitivesTest.cpp b/tests/PDFPrimitivesTest.cpp
index 9ca1bd619a23c1c4cb8af0599729db5a548263b3..952e49994ad3c0723b96ed41f77602ec49c56fbd 100644
--- a/tests/PDFPrimitivesTest.cpp
+++ b/tests/PDFPrimitivesTest.cpp
@@ -18,6 +18,7 @@
 #include "SkPDFFont.h"
 #include "SkPDFStream.h"
 #include "SkPDFTypes.h"
+#include "SkPDFUtils.h"
 #include "SkReadBuffer.h"
 #include "SkScalar.h"
 #include "SkStream.h"
@@ -341,7 +342,7 @@ static void TestPDFDict(skiatest::Reporter* reporter) {
 
     dict.reset(new SkPDFDict("DType"));
     ASSERT_EMIT_EQ(reporter, *dict, "<</Type /DType>>");
-    
+
     SkAutoTUnref<SkPDFArray> referencedArray(new SkPDFArray);
     Catalog catalog;
     catalog.numbers.addObject(referencedArray.get());
@@ -435,3 +436,52 @@ DEF_TEST(PDFFontCanEmbedTypeface, reporter) {
     REPORTER_ASSERT(reporter,
                     SkPDFFont::CanEmbedTypeface(portableTypeface, &canon));
 }
+
+
+// test to see that all finite scalars round trip via scanf().
+static void check_pdf_scalar_serialization(skiatest::Reporter* reporter,
+                                           float inputFloat) {
+    SkDynamicMemoryWStream buffer;
+    SkPDFUtils::AppendScalar(inputFloat, &buffer);
+    char floatString[2048];
+    if (buffer.bytesWritten() >= sizeof(floatString)) {
+        ERRORF(reporter, "absurdly long output.");
+        return;
+    }
+    buffer.copyTo(floatString);
+    floatString[buffer.bytesWritten()] = '\0';
+    if (reporter->verbose()) {
+        SkDebugf("%.9g = \"%s\"\n", inputFloat, floatString);
+    }
+    float roundTripFloat;
+    if (1 != sscanf(floatString, "%f", &roundTripFloat)) {
+        ERRORF(reporter, "unscannable result");
+        return;
+    }
+    if (isfinite(inputFloat)) {
+        REPORTER_ASSERT(reporter, roundTripFloat == inputFloat);
+    }
+}
+
+// Test SkPDFUtils::AppendScalar for accuracy.
+DEF_TEST(PDFPrimitives_Scalar, reporter) {
+    const int kRandomSeed = 0xBEEF;
+    int iterationCount = 500;
+    SkRandom random(kRandomSeed);
+    while (iterationCount-- > 0) {
+        union {
+            float inputFloat;
+            uint32_t u;
+        };
+        static_assert(sizeof(float) == sizeof(uint32_t), "");
+        u = random.nextU();  // Pick any random float.
+        check_pdf_scalar_serialization(reporter, inputFloat);
+    }
+    float alwaysCheck[] = { 0.0f, -0.0f, 1.0f, -1.0f, FLT_MIN, FLT_MAX,
+                            -FLT_MIN, -FLT_MAX, SK_FloatInfinity,
+                            SK_FloatNegativeInfinity, SK_FloatNaN, SK_ScalarPI,
+                            static_cast<float>(1.0 / 10.0)};
+    for (float inputFloat: alwaysCheck) {
+        check_pdf_scalar_serialization(reporter, inputFloat);
+    }
+}