[libc++] Fix leading zeros in std::to_chars
Summary:
It is a bugfix proposal for https://bugs.llvm.org/show_bug.cgi?id=42166.
`std::to_chars` appends leading zeros if input 64-bit value has 9, 10 or 11 digits.
According to documentation `std::to_chars` must not append leading zeros:
https://en.cppreference.com/w/cpp/utility/to_chars
Changeset should not affect `std::to_chars` performance:
http://quick-bench.com/CEpRs14xxA9WLvkXFtaJ3TWOVAg
Unit test that `std::from_chars` supports compatibility for both `std::to_chars` outputs (previous and fixed one) already exists:
https://github.com/llvm-mirror/libcxx/blob/1f60111b597e5cb80a4513ec86f79b7e137f7793/test/std/utilities/charconv/charconv.from.chars/integral.pass.cpp#L63
Reviewers: lichray, mclow.lists, ldionne, EricWF
Reviewed By: lichray, mclow.lists
Subscribers: zoecarver, christof, dexonsmith, libcxx-commits
Differential Revision: https://reviews.llvm.org/D63047
llvm-svn: 362967
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 6bc4a7685ee4321a74ad987032e678c6273775ff
diff --git a/src/charconv.cpp b/src/charconv.cpp
index 6ea473b..d303588 100644
--- a/src/charconv.cpp
+++ b/src/charconv.cpp
@@ -60,48 +60,50 @@
return append2(append2(buffer, (i) / 100), (i) % 100);
}
+template <typename T>
+inline _LIBCPP_INLINE_VISIBILITY char*
+append2_no_zeros(char* buffer, T v)
+{
+ if (v < 10)
+ return append1(buffer, v);
+ else
+ return append2(buffer, v);
+}
+
+template <typename T>
+inline _LIBCPP_INLINE_VISIBILITY char*
+append4_no_zeros(char* buffer, T v)
+{
+ if (v < 100)
+ return append2_no_zeros(buffer, v);
+ else if (v < 1000)
+ return append3(buffer, v);
+ else
+ return append4(buffer, v);
+}
+
+template <typename T>
+inline _LIBCPP_INLINE_VISIBILITY char*
+append8_no_zeros(char* buffer, T v)
+{
+ if (v < 10000)
+ {
+ buffer = append4_no_zeros(buffer, v);
+ }
+ else
+ {
+ buffer = append4_no_zeros(buffer, v / 10000);
+ buffer = append4(buffer, v % 10000);
+ }
+ return buffer;
+}
+
char*
__u32toa(uint32_t value, char* buffer)
{
- if (value < 10000)
+ if (value < 100000000)
{
- if (value < 100)
- {
- if (value < 10)
- buffer = append1(buffer, value);
- else
- buffer = append2(buffer, value);
- }
- else
- {
- if (value < 1000)
- buffer = append3(buffer, value);
- else
- buffer = append4(buffer, value);
- }
- }
- else if (value < 100000000)
- {
- // value = bbbbcccc
- const uint32_t b = value / 10000;
- const uint32_t c = value % 10000;
-
- if (value < 1000000)
- {
- if (value < 100000)
- buffer = append1(buffer, b);
- else
- buffer = append2(buffer, b);
- }
- else
- {
- if (value < 10000000)
- buffer = append3(buffer, b);
- else
- buffer = append4(buffer, b);
- }
-
- buffer = append4(buffer, c);
+ buffer = append8_no_zeros(buffer, value);
}
else
{
@@ -109,11 +111,7 @@
const uint32_t a = value / 100000000; // 1 to 42
value %= 100000000;
- if (a < 10)
- buffer = append1(buffer, a);
- else
- buffer = append2(buffer, a);
-
+ buffer = append2_no_zeros(buffer, a);
buffer = append4(buffer, value / 10000);
buffer = append4(buffer, value % 10000);
}
@@ -127,71 +125,14 @@
if (value < 100000000)
{
uint32_t v = static_cast<uint32_t>(value);
- if (v < 10000)
- {
- if (v < 100)
- {
- if (v < 10)
- buffer = append1(buffer, v);
- else
- buffer = append2(buffer, v);
- }
- else
- {
- if (v < 1000)
- buffer = append3(buffer, v);
- else
- buffer = append4(buffer, v);
- }
- }
- else
- {
- // value = bbbbcccc
- const uint32_t b = v / 10000;
- const uint32_t c = v % 10000;
-
- if (v < 1000000)
- {
- if (v < 100000)
- buffer = append1(buffer, b);
- else
- buffer = append2(buffer, b);
- }
- else
- {
- if (v < 10000000)
- buffer = append3(buffer, b);
- else
- buffer = append4(buffer, b);
- }
-
- buffer = append4(buffer, c);
- }
+ buffer = append8_no_zeros(buffer, v);
}
else if (value < 10000000000000000)
{
const uint32_t v0 = static_cast<uint32_t>(value / 100000000);
const uint32_t v1 = static_cast<uint32_t>(value % 100000000);
- const uint32_t b0 = v0 / 10000;
- const uint32_t c0 = v0 % 10000;
-
- if (v0 < 1000000)
- {
- if (v0 < 100000)
- buffer = append1(buffer, b0);
- else
- buffer = append2(buffer, b0);
- }
- else
- {
- if (v0 < 10000000)
- buffer = append3(buffer, b0);
- else
- buffer = append4(buffer, b0);
- }
-
- buffer = append4(buffer, c0);
+ buffer = append8_no_zeros(buffer, v0);
buffer = append4(buffer, v1 / 10000);
buffer = append4(buffer, v1 % 10000);
}
@@ -201,20 +142,7 @@
static_cast<uint32_t>(value / 10000000000000000); // 1 to 1844
value %= 10000000000000000;
- if (a < 100)
- {
- if (a < 10)
- buffer = append1(buffer, a);
- else
- buffer = append2(buffer, a);
- }
- else
- {
- if (a < 1000)
- buffer = append3(buffer, a);
- else
- buffer = append4(buffer, a);
- }
+ buffer = append4_no_zeros(buffer, a);
const uint32_t v0 = static_cast<uint32_t>(value / 100000000);
const uint32_t v1 = static_cast<uint32_t>(value % 100000000);