[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
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@362967 91177308-0d34-0410-b5e6-96231b3b80d8
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);
diff --git a/test/std/utilities/charconv/charconv.to.chars/integral.pass.cpp b/test/std/utilities/charconv/charconv.to.chars/integral.pass.cpp
index 4bfe27d..e30d3c8 100644
--- a/test/std/utilities/charconv/charconv.to.chars/integral.pass.cpp
+++ b/test/std/utilities/charconv/charconv.to.chars/integral.pass.cpp
@@ -45,6 +45,56 @@
test(0xdeadbeaf, "deadbeaf", 16);
test(0755, "755", 8);
+ // Test each len till len of UINT64_MAX = 20 because to_chars algorithm
+ // makes branches based on decimal digits count in the value string
+ // representation.
+ // Test driver automatically skips values not fitting into source type.
+ test(1UL, "1");
+ test(12UL, "12");
+ test(123UL, "123");
+ test(1234UL, "1234");
+ test(12345UL, "12345");
+ test(123456UL, "123456");
+ test(1234567UL, "1234567");
+ test(12345678UL, "12345678");
+ test(123456789UL, "123456789");
+ test(1234567890UL, "1234567890");
+ test(12345678901UL, "12345678901");
+ test(123456789012UL, "123456789012");
+ test(1234567890123UL, "1234567890123");
+ test(12345678901234UL, "12345678901234");
+ test(123456789012345UL, "123456789012345");
+ test(1234567890123456UL, "1234567890123456");
+ test(12345678901234567UL, "12345678901234567");
+ test(123456789012345678UL, "123456789012345678");
+ test(1234567890123456789UL, "1234567890123456789");
+ test(12345678901234567890UL, "12345678901234567890");
+
+ // Test special cases with zeros inside a value string representation,
+ // to_chars algorithm processes them in a special way and should not
+ // skip trailing zeros
+ // Test driver automatically skips values not fitting into source type.
+ test(0UL, "0");
+ test(10UL, "10");
+ test(100UL, "100");
+ test(1000UL, "1000");
+ test(10000UL, "10000");
+ test(100000UL, "100000");
+ test(1000000UL, "1000000");
+ test(10000000UL, "10000000");
+ test(100000000UL, "100000000");
+ test(1000000000UL, "1000000000");
+ test(10000000000UL, "10000000000");
+ test(100000000000UL, "100000000000");
+ test(1000000000000UL, "1000000000000");
+ test(10000000000000UL, "10000000000000");
+ test(100000000000000UL, "100000000000000");
+ test(1000000000000000UL, "1000000000000000");
+ test(10000000000000000UL, "10000000000000000");
+ test(100000000000000000UL, "100000000000000000");
+ test(1000000000000000000UL, "1000000000000000000");
+ test(10000000000000000000UL, "10000000000000000000");
+
for (int b = 2; b < 37; ++b)
{
using xl = std::numeric_limits<T>;
@@ -73,6 +123,53 @@
test(-2647, "-101001010111", 2);
test(-0xcc1, "-cc1", 16);
+ // Test each len till len of INT64_MAX = 19 because to_chars algorithm
+ // makes branches based on decimal digits count in the value string
+ // representation.
+ // Test driver automatically skips values not fitting into source type.
+ test(-1L, "-1");
+ test(-12L, "-12");
+ test(-123L, "-123");
+ test(-1234L, "-1234");
+ test(-12345L, "-12345");
+ test(-123456L, "-123456");
+ test(-1234567L, "-1234567");
+ test(-12345678L, "-12345678");
+ test(-123456789L, "-123456789");
+ test(-1234567890L, "-1234567890");
+ test(-12345678901L, "-12345678901");
+ test(-123456789012L, "-123456789012");
+ test(-1234567890123L, "-1234567890123");
+ test(-12345678901234L, "-12345678901234");
+ test(-123456789012345L, "-123456789012345");
+ test(-1234567890123456L, "-1234567890123456");
+ test(-12345678901234567L, "-12345678901234567");
+ test(-123456789012345678L, "-123456789012345678");
+ test(-1234567890123456789L, "-1234567890123456789");
+
+ // Test special cases with zeros inside a value string representation,
+ // to_chars algorithm processes them in a special way and should not
+ // skip trailing zeros
+ // Test driver automatically skips values not fitting into source type.
+ test(-10L, "-10");
+ test(-100L, "-100");
+ test(-1000L, "-1000");
+ test(-10000L, "-10000");
+ test(-100000L, "-100000");
+ test(-1000000L, "-1000000");
+ test(-10000000L, "-10000000");
+ test(-100000000L, "-100000000");
+ test(-1000000000L, "-1000000000");
+ test(-10000000000L, "-10000000000");
+ test(-100000000000L, "-100000000000");
+ test(-1000000000000L, "-1000000000000");
+ test(-10000000000000L, "-10000000000000");
+ test(-100000000000000L, "-100000000000000");
+ test(-1000000000000000L, "-1000000000000000");
+ test(-10000000000000000L, "-10000000000000000");
+ test(-100000000000000000L, "-100000000000000000");
+ test(-1000000000000000000L, "-1000000000000000000");
+
for (int b = 2; b < 37; ++b)
{
using xl = std::numeric_limits<T>;
