Skip to content

A
abseil-cpp
Commit b2a6c1bc by Derek Mauro Committed by Copybara-Service
Options

Cleanup `//absl/strings/internal/memutil.h` 

`memmatch()` is only used in `string_view.cc`, so move it there.
The moving of `memmatch()` to `string_view.cc` decouples `string_view`
from `memutil`, which will allow us to move `string_view` into its
own target in a followup.

The only other function that is used is `memcasecmp()`, so delete
all other functions.

PiperOrigin-RevId: 547238386
Change-Id: Id6fad47dd24191c8e8f26dd923fffa1007c8db4a
parent 20cf119d
Showing with 34 additions and 528 deletions
absl/strings/internal/memutil.cc
...@@ -16,6 +16,8 @@ ...@@ -16,6 +16,8 @@
#include <cstdlib> #include <cstdlib>
#include "absl/strings/ascii.h"
namespace absl { namespace absl {
ABSL_NAMESPACE_BEGIN ABSL_NAMESPACE_BEGIN
namespace strings_internal { namespace strings_internal {
...@@ -33,83 +35,6 @@ int memcasecmp(const char* s1, const char* s2, size_t len) { ...@@ -33,83 +35,6 @@ int memcasecmp(const char* s1, const char* s2, size_t len) {
return 0; return 0;
} }
char* memdup(const char* s, size_t slen) {
void* copy;
if ((copy = malloc(slen)) == nullptr) return nullptr;
memcpy(copy, s, slen);
return reinterpret_cast<char*>(copy);
}
char* memrchr(const char* s, int c, size_t slen) {
for (const char* e = s + slen - 1; e >= s; e--) {
if (*e == c) return const_cast<char*>(e);
}
return nullptr;
}
size_t memspn(const char* s, size_t slen, const char* accept) {
const char* p = s;
const char* spanp;
char c, sc;
cont:
c = *p++;
if (slen-- == 0)
return static_cast<size_t>(p - 1 - s);
for (spanp = accept; (sc = *spanp++) != '\0';)
if (sc == c) goto cont;
return static_cast<size_t>(p - 1 - s);
}
size_t memcspn(const char* s, size_t slen, const char* reject) {
const char* p = s;
const char* spanp;
char c, sc;
while (slen-- != 0) {
c = *p++;
for (spanp = reject; (sc = *spanp++) != '\0';)
if (sc == c)
return static_cast<size_t>(p - 1 - s);
}
return static_cast<size_t>(p - s);
}
char* mempbrk(const char* s, size_t slen, const char* accept) {
const char* scanp;
int sc;
for (; slen; ++s, --slen) {
for (scanp = accept; (sc = *scanp++) != '\0';)
if (sc == *s) return const_cast<char*>(s);
}
return nullptr;
}
// This is significantly faster for case-sensitive matches with very
// few possible matches. See unit test for benchmarks.
const char* memmatch(const char* phaystack, size_t haylen, const char* pneedle,
size_t neelen) {
if (0 == neelen) {
return phaystack; // even if haylen is 0
}
if (haylen < neelen) return nullptr;
const char* match;
const char* hayend = phaystack + haylen - neelen + 1;
// A static cast is used here to work around the fact that memchr returns
// a void* on Posix-compliant systems and const void* on Windows.
while (
(match = static_cast<const char*>(memchr(
phaystack, pneedle[0], static_cast<size_t>(hayend - phaystack))))) {
if (memcmp(match, pneedle, neelen) == 0)
return match;
else
phaystack = match + 1;
}
return nullptr;
}
} // namespace strings_internal } // namespace strings_internal
ABSL_NAMESPACE_END ABSL_NAMESPACE_END
} // namespace absl } // namespace absl
absl/strings/internal/memutil.h
...@@ -14,51 +14,6 @@ ...@@ -14,51 +14,6 @@
// limitations under the License. // limitations under the License.
// //
// These routines provide mem versions of standard C string routines,
// such as strpbrk. They function exactly the same as the str versions,
// so if you wonder what they are, replace the word "mem" by
// "str" and check out the man page. I could return void*, as the
// strutil.h mem*() routines tend to do, but I return char* instead
// since this is by far the most common way these functions are called.
//
// The difference between the mem and str versions is the mem version
// takes a pointer and a length, rather than a '\0'-terminated string.
// The memcase* routines defined here assume the locale is "C"
// (they use absl::ascii_tolower instead of tolower).
//
// These routines are based on the BSD library.
//
// Here's a list of routines from string.h, and their mem analogues.
// Functions in lowercase are defined in string.h; those in UPPERCASE
// are defined here:
//
// strlen --
// strcat strncat MEMCAT
// strcpy strncpy memcpy
// -- memccpy (very cool function, btw)
// -- memmove
// -- memset
// strcmp strncmp memcmp
// strcasecmp strncasecmp MEMCASECMP
// strchr memchr
// strcoll --
// strxfrm --
// strdup strndup MEMDUP
// strrchr MEMRCHR
// strspn MEMSPN
// strcspn MEMCSPN
// strpbrk MEMPBRK
// strstr MEMSTR MEMMEM
// (g)strcasestr MEMCASESTR MEMCASEMEM
// strtok --
// strprefix MEMPREFIX (strprefix is from strutil.h)
// strcaseprefix MEMCASEPREFIX (strcaseprefix is from strutil.h)
// strsuffix MEMSUFFIX (strsuffix is from strutil.h)
// strcasesuffix MEMCASESUFFIX (strcasesuffix is from strutil.h)
// -- MEMIS
// -- MEMCASEIS
// strcount MEMCOUNT (strcount is from strutil.h)
#ifndef ABSL_STRINGS_INTERNAL_MEMUTIL_H_ #ifndef ABSL_STRINGS_INTERNAL_MEMUTIL_H_
#define ABSL_STRINGS_INTERNAL_MEMUTIL_H_ #define ABSL_STRINGS_INTERNAL_MEMUTIL_H_
...@@ -72,74 +27,11 @@ namespace absl { ...@@ -72,74 +27,11 @@ namespace absl {
ABSL_NAMESPACE_BEGIN ABSL_NAMESPACE_BEGIN
namespace strings_internal { namespace strings_internal {
inline char* memcat(char* dest, size_t destlen, const char* src, // Performs a byte-by-byte comparison of `len` bytes of the strings `s1` and
size_t srclen) { // `s2`, ignoring the case of the characters. It returns an integer less than,
return reinterpret_cast<char*>(memcpy(dest + destlen, src, srclen)); // equal to, or greater than zero if `s1` is found, respectively, to be less
} // than, to match, or be greater than `s2`.
int memcasecmp(const char* s1, const char* s2, size_t len); int memcasecmp(const char* s1, const char* s2, size_t len);
char* memdup(const char* s, size_t slen);
char* memrchr(const char* s, int c, size_t slen);
size_t memspn(const char* s, size_t slen, const char* accept);
size_t memcspn(const char* s, size_t slen, const char* reject);
char* mempbrk(const char* s, size_t slen, const char* accept);
// This is for internal use only. Don't call this directly
template <bool case_sensitive>
const char* int_memmatch(const char* haystack, size_t haylen,
const char* needle, size_t neelen) {
if (0 == neelen) {
return haystack; // even if haylen is 0
}
const char* hayend = haystack + haylen;
const char* needlestart = needle;
const char* needleend = needlestart + neelen;
for (; haystack < hayend; ++haystack) {
char hay = case_sensitive
? *haystack
: absl::ascii_tolower(static_cast<unsigned char>(*haystack));
char nee = case_sensitive
? *needle
: absl::ascii_tolower(static_cast<unsigned char>(*needle));
if (hay == nee) {
if (++needle == needleend) {
return haystack + 1 - neelen;
}
} else if (needle != needlestart) {
// must back up haystack in case a prefix matched (find "aab" in "aaab")
haystack -= needle - needlestart; // for loop will advance one more
needle = needlestart;
}
}
return nullptr;
}
// These are the guys you can call directly
inline const char* memstr(const char* phaystack, size_t haylen,
const char* pneedle) {
return int_memmatch<true>(phaystack, haylen, pneedle, strlen(pneedle));
}
inline const char* memcasestr(const char* phaystack, size_t haylen,
const char* pneedle) {
return int_memmatch<false>(phaystack, haylen, pneedle, strlen(pneedle));
}
inline const char* memmem(const char* phaystack, size_t haylen,
const char* pneedle, size_t needlelen) {
return int_memmatch<true>(phaystack, haylen, pneedle, needlelen);
}
inline const char* memcasemem(const char* phaystack, size_t haylen,
const char* pneedle, size_t needlelen) {
return int_memmatch<false>(phaystack, haylen, pneedle, needlelen);
}
// This is significantly faster for case-sensitive matches with very
// few possible matches. See unit test for benchmarks.
const char* memmatch(const char* phaystack, size_t haylen, const char* pneedle,
size_t neelen);
} // namespace strings_internal } // namespace strings_internal
ABSL_NAMESPACE_END ABSL_NAMESPACE_END
......
absl/strings/internal/memutil_benchmark.cc
...@@ -25,62 +25,6 @@ ...@@ -25,62 +25,6 @@
// - an easy search: 'b' // - an easy search: 'b'
// - a medium search: 'ab'. That means every letter is a possible match. // - a medium search: 'ab'. That means every letter is a possible match.
// - a pathological search: 'aaaaaa.......aaaaab' (half as many a's as haytack) // - a pathological search: 'aaaaaa.......aaaaab' (half as many a's as haytack)
// We benchmark case-sensitive and case-insensitive versions of
// three memmem implementations:
// - memmem() from memutil.h
// - search() from STL
// - memmatch(), a custom implementation using memchr and memcmp.
// Here are sample results:
//
// Run on (12 X 3800 MHz CPU s)
// CPU Caches:
// L1 Data 32K (x6)
// L1 Instruction 32K (x6)
// L2 Unified 256K (x6)
// L3 Unified 15360K (x1)
// ----------------------------------------------------------------
// Benchmark Time CPU Iterations
// ----------------------------------------------------------------
// BM_Memmem 3583 ns 3582 ns 196469 2.59966GB/s
// BM_MemmemMedium 13743 ns 13742 ns 50901 693.986MB/s
// BM_MemmemPathological 13695030 ns 13693977 ns 51 713.133kB/s
// BM_Memcasemem 3299 ns 3299 ns 212942 2.82309GB/s
// BM_MemcasememMedium 16407 ns 16406 ns 42170 581.309MB/s
// BM_MemcasememPathological 17267745 ns 17266030 ns 41 565.598kB/s
// BM_Search 1610 ns 1609 ns 431321 5.78672GB/s
// BM_SearchMedium 11111 ns 11110 ns 63001 858.414MB/s
// BM_SearchPathological 12117390 ns 12116397 ns 58 805.984kB/s
// BM_Searchcase 3081 ns 3081 ns 229949 3.02313GB/s
// BM_SearchcaseMedium 16003 ns 16001 ns 44170 595.998MB/s
// BM_SearchcasePathological 15823413 ns 15821909 ns 44 617.222kB/s
// BM_Memmatch 197 ns 197 ns 3584225 47.2951GB/s
// BM_MemmatchMedium 52333 ns 52329 ns 13280 182.244MB/s
// BM_MemmatchPathological 659799 ns 659727 ns 1058 14.4556MB/s
// BM_Memcasematch 5460 ns 5460 ns 127606 1.70586GB/s
// BM_MemcasematchMedium 32861 ns 32857 ns 21258 290.248MB/s
// BM_MemcasematchPathological 15154243 ns 15153089 ns 46 644.464kB/s
// BM_MemmemStartup 5 ns 5 ns 150821500
// BM_SearchStartup 5 ns 5 ns 150644203
// BM_MemmatchStartup 7 ns 7 ns 97068802
//
// Conclusions:
//
// The following recommendations are based on the sample results above. However,
// we have found that the performance of STL search can vary significantly
// depending on compiler and standard library implementation. We recommend you
// run the benchmarks for yourself on relevant platforms.
//
// If you need case-insensitive, STL search is slightly better than memmem for
// all cases.
//
// Case-sensitive is more subtle:
// Custom memmatch is _very_ fast at scanning, so if you have very few possible
// matches in your haystack, that's the way to go. Performance drops
// significantly with more matches.
//
// STL search is slightly faster than memmem in the medium and pathological
// benchmarks. However, the performance of memmem is currently more dependable
// across platforms and build configurations.
namespace { namespace {
...@@ -94,96 +38,10 @@ const char* MakeHaystack() { ...@@ -94,96 +38,10 @@ const char* MakeHaystack() {
} }
const char* const kHaystack = MakeHaystack(); const char* const kHaystack = MakeHaystack();
void BM_Memmem(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(
absl::strings_internal::memmem(kHaystack, kHaystackSize, "b", 1));
}
state.SetBytesProcessed(kHaystackSize64 * state.iterations());
}
BENCHMARK(BM_Memmem);
void BM_MemmemMedium(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(
absl::strings_internal::memmem(kHaystack, kHaystackSize, "ab", 2));
}
state.SetBytesProcessed(kHaystackSize64 * state.iterations());
}
BENCHMARK(BM_MemmemMedium);
void BM_MemmemPathological(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(absl::strings_internal::memmem(
kHaystack, kHaystackSize, kHaystack + kHaystackSize / 2,
kHaystackSize - kHaystackSize / 2));
}
state.SetBytesProcessed(kHaystackSize64 * state.iterations());
}
BENCHMARK(BM_MemmemPathological);
void BM_Memcasemem(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(
absl::strings_internal::memcasemem(kHaystack, kHaystackSize, "b", 1));
}
state.SetBytesProcessed(kHaystackSize64 * state.iterations());
}
BENCHMARK(BM_Memcasemem);
void BM_MemcasememMedium(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(
absl::strings_internal::memcasemem(kHaystack, kHaystackSize, "ab", 2));
}
state.SetBytesProcessed(kHaystackSize64 * state.iterations());
}
BENCHMARK(BM_MemcasememMedium);
void BM_MemcasememPathological(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(absl::strings_internal::memcasemem(
kHaystack, kHaystackSize, kHaystack + kHaystackSize / 2,
kHaystackSize - kHaystackSize / 2));
}
state.SetBytesProcessed(kHaystackSize64 * state.iterations());
}
BENCHMARK(BM_MemcasememPathological);
bool case_eq(const char a, const char b) { bool case_eq(const char a, const char b) {
return absl::ascii_tolower(a) == absl::ascii_tolower(b); return absl::ascii_tolower(a) == absl::ascii_tolower(b);
} }
void BM_Search(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(std::search(kHaystack, kHaystack + kHaystackSize,
kHaystack + kHaystackSize - 1,
kHaystack + kHaystackSize));
}
state.SetBytesProcessed(kHaystackSize64 * state.iterations());
}
BENCHMARK(BM_Search);
void BM_SearchMedium(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(std::search(kHaystack, kHaystack + kHaystackSize,
kHaystack + kHaystackSize - 2,
kHaystack + kHaystackSize));
}
state.SetBytesProcessed(kHaystackSize64 * state.iterations());
}
BENCHMARK(BM_SearchMedium);
void BM_SearchPathological(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(std::search(kHaystack, kHaystack + kHaystackSize,
kHaystack + kHaystackSize / 2,
kHaystack + kHaystackSize));
}
state.SetBytesProcessed(kHaystackSize64 * state.iterations());
}
BENCHMARK(BM_SearchPathological);
void BM_Searchcase(benchmark::State& state) { void BM_Searchcase(benchmark::State& state) {
for (auto _ : state) { for (auto _ : state) {
benchmark::DoNotOptimize(std::search(kHaystack, kHaystack + kHaystackSize, benchmark::DoNotOptimize(std::search(kHaystack, kHaystack + kHaystackSize,
...@@ -241,34 +99,6 @@ const char* memcasematch(const char* phaystack, size_t haylen, ...@@ -241,34 +99,6 @@ const char* memcasematch(const char* phaystack, size_t haylen,
return nullptr; return nullptr;
} }
void BM_Memmatch(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(
absl::strings_internal::memmatch(kHaystack, kHaystackSize, "b", 1));
}
state.SetBytesProcessed(kHaystackSize64 * state.iterations());
}
BENCHMARK(BM_Memmatch);
void BM_MemmatchMedium(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(
absl::strings_internal::memmatch(kHaystack, kHaystackSize, "ab", 2));
}
state.SetBytesProcessed(kHaystackSize64 * state.iterations());
}
BENCHMARK(BM_MemmatchMedium);
void BM_MemmatchPathological(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(absl::strings_internal::memmatch(
kHaystack, kHaystackSize, kHaystack + kHaystackSize / 2,
kHaystackSize - kHaystackSize / 2));
}
state.SetBytesProcessed(kHaystackSize64 * state.iterations());
}
BENCHMARK(BM_MemmatchPathological);
void BM_Memcasematch(benchmark::State& state) { void BM_Memcasematch(benchmark::State& state) {
for (auto _ : state) { for (auto _ : state) {
benchmark::DoNotOptimize(memcasematch(kHaystack, kHaystackSize, "b", 1)); benchmark::DoNotOptimize(memcasematch(kHaystack, kHaystackSize, "b", 1));
...@@ -295,29 +125,4 @@ void BM_MemcasematchPathological(benchmark::State& state) { ...@@ -295,29 +125,4 @@ void BM_MemcasematchPathological(benchmark::State& state) {
} }
BENCHMARK(BM_MemcasematchPathological); BENCHMARK(BM_MemcasematchPathological);
void BM_MemmemStartup(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(absl::strings_internal::memmem(
kHaystack + kHaystackSize - 10, 10, kHaystack + kHaystackSize - 1, 1));
}
}
BENCHMARK(BM_MemmemStartup);
void BM_SearchStartup(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(
std::search(kHaystack + kHaystackSize - 10, kHaystack + kHaystackSize,
kHaystack + kHaystackSize - 1, kHaystack + kHaystackSize));
}
}
BENCHMARK(BM_SearchStartup);
void BM_MemmatchStartup(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(absl::strings_internal::memmatch(
kHaystack + kHaystackSize - 10, 10, kHaystack + kHaystackSize - 1, 1));
}
}
BENCHMARK(BM_MemmatchStartup);
} // namespace } // namespace
absl/strings/internal/memutil_test.cc
...@@ -19,42 +19,12 @@ ...@@ -19,42 +19,12 @@
#include <cstdlib> #include <cstdlib>
#include "gtest/gtest.h" #include "gtest/gtest.h"
#include "absl/strings/ascii.h"
namespace { namespace {
static char* memcasechr(const char* s, int c, size_t slen) { TEST(MemUtil, memcasecmp) {
c = absl::ascii_tolower(c);
for (; slen; ++s, --slen) {
if (absl::ascii_tolower(*s) == c) return const_cast<char*>(s);
}
return nullptr;
}
static const char* memcasematch(const char* phaystack, size_t haylen,
const char* pneedle, size_t neelen) {
if (0 == neelen) {
return phaystack; // even if haylen is 0
}
if (haylen < neelen) return nullptr;
const char* match;
const char* hayend = phaystack + haylen - neelen + 1;
while ((match = static_cast<char*>(
memcasechr(phaystack, pneedle[0], hayend - phaystack)))) {
if (absl::strings_internal::memcasecmp(match, pneedle, neelen) == 0)
return match;
else
phaystack = match + 1;
}
return nullptr;
}
TEST(MemUtilTest, AllTests) {
// check memutil functions // check memutil functions
char a[1000]; const char a[] = "hello there";
absl::strings_internal::memcat(a, 0, "hello", sizeof("hello") - 1);
absl::strings_internal::memcat(a, 5, " there", sizeof(" there") - 1);
EXPECT_EQ(absl::strings_internal::memcasecmp(a, "heLLO there", EXPECT_EQ(absl::strings_internal::memcasecmp(a, "heLLO there",
sizeof("hello there") - 1), sizeof("hello there") - 1),
...@@ -66,114 +36,6 @@ TEST(MemUtilTest, AllTests) { ...@@ -66,114 +36,6 @@ TEST(MemUtilTest, AllTests) {
sizeof("hello there") - 2), sizeof("hello there") - 2),
0); 0);
EXPECT_EQ(absl::strings_internal::memcasecmp(a, "whatever", 0), 0); EXPECT_EQ(absl::strings_internal::memcasecmp(a, "whatever", 0), 0);
char* p = absl::strings_internal::memdup("hello", 5);
free(p);
p = absl::strings_internal::memrchr("hello there", 'e',
sizeof("hello there") - 1);
EXPECT_TRUE(p && p[-1] == 'r');
p = absl::strings_internal::memrchr("hello there", 'e',
sizeof("hello there") - 2);
EXPECT_TRUE(p && p[-1] == 'h');
p = absl::strings_internal::memrchr("hello there", 'u',
sizeof("hello there") - 1);
EXPECT_TRUE(p == nullptr);
int len = absl::strings_internal::memspn("hello there",
sizeof("hello there") - 1, "hole");
EXPECT_EQ(len, sizeof("hello") - 1);
len = absl::strings_internal::memspn("hello there", sizeof("hello there") - 1,
"u");
EXPECT_EQ(len, 0);
len = absl::strings_internal::memspn("hello there", sizeof("hello there") - 1,
"");
EXPECT_EQ(len, 0);
len = absl::strings_internal::memspn("hello there", sizeof("hello there") - 1,
"trole h");
EXPECT_EQ(len, sizeof("hello there") - 1);
len = absl::strings_internal::memspn("hello there!",
sizeof("hello there!") - 1, "trole h");
EXPECT_EQ(len, sizeof("hello there") - 1);
len = absl::strings_internal::memspn("hello there!",
sizeof("hello there!") - 2, "trole h!");
EXPECT_EQ(len, sizeof("hello there!") - 2);
len = absl::strings_internal::memcspn("hello there",
sizeof("hello there") - 1, "leho");
EXPECT_EQ(len, 0);
len = absl::strings_internal::memcspn("hello there",
sizeof("hello there") - 1, "u");
EXPECT_EQ(len, sizeof("hello there") - 1);
len = absl::strings_internal::memcspn("hello there",
sizeof("hello there") - 1, "");
EXPECT_EQ(len, sizeof("hello there") - 1);
len = absl::strings_internal::memcspn("hello there",
sizeof("hello there") - 1, " ");
EXPECT_EQ(len, 5);
p = absl::strings_internal::mempbrk("hello there", sizeof("hello there") - 1,
"leho");
EXPECT_TRUE(p && p[1] == 'e' && p[2] == 'l');
p = absl::strings_internal::mempbrk("hello there", sizeof("hello there") - 1,
"nu");
EXPECT_TRUE(p == nullptr);
p = absl::strings_internal::mempbrk("hello there!",
sizeof("hello there!") - 2, "!");
EXPECT_TRUE(p == nullptr);
p = absl::strings_internal::mempbrk("hello there", sizeof("hello there") - 1,
" t ");
EXPECT_TRUE(p && p[-1] == 'o' && p[1] == 't');
{
const char kHaystack[] = "0123456789";
EXPECT_EQ(absl::strings_internal::memmem(kHaystack, 0, "", 0), kHaystack);
EXPECT_EQ(absl::strings_internal::memmem(kHaystack, 10, "012", 3),
kHaystack);
EXPECT_EQ(absl::strings_internal::memmem(kHaystack, 10, "0xx", 1),
kHaystack);
EXPECT_EQ(absl::strings_internal::memmem(kHaystack, 10, "789", 3),
kHaystack + 7);
EXPECT_EQ(absl::strings_internal::memmem(kHaystack, 10, "9xx", 1),
kHaystack + 9);
EXPECT_TRUE(absl::strings_internal::memmem(kHaystack, 10, "9xx", 3) ==
nullptr);
EXPECT_TRUE(absl::strings_internal::memmem(kHaystack, 10, "xxx", 1) ==
nullptr);
}
{
const char kHaystack[] = "aBcDeFgHiJ";
EXPECT_EQ(absl::strings_internal::memcasemem(kHaystack, 0, "", 0),
kHaystack);
EXPECT_EQ(absl::strings_internal::memcasemem(kHaystack, 10, "Abc", 3),
kHaystack);
EXPECT_EQ(absl::strings_internal::memcasemem(kHaystack, 10, "Axx", 1),
kHaystack);
EXPECT_EQ(absl::strings_internal::memcasemem(kHaystack, 10, "hIj", 3),
kHaystack + 7);
EXPECT_EQ(absl::strings_internal::memcasemem(kHaystack, 10, "jxx", 1),
kHaystack + 9);
EXPECT_TRUE(absl::strings_internal::memcasemem(kHaystack, 10, "jxx", 3) ==
nullptr);
EXPECT_TRUE(absl::strings_internal::memcasemem(kHaystack, 10, "xxx", 1) ==
nullptr);
}
{
const char kHaystack[] = "0123456789";
EXPECT_EQ(absl::strings_internal::memmatch(kHaystack, 0, "", 0), kHaystack);
EXPECT_EQ(absl::strings_internal::memmatch(kHaystack, 10, "012", 3),
kHaystack);
EXPECT_EQ(absl::strings_internal::memmatch(kHaystack, 10, "0xx", 1),
kHaystack);
EXPECT_EQ(absl::strings_internal::memmatch(kHaystack, 10, "789", 3),
kHaystack + 7);
EXPECT_EQ(absl::strings_internal::memmatch(kHaystack, 10, "9xx", 1),
kHaystack + 9);
EXPECT_TRUE(absl::strings_internal::memmatch(kHaystack, 10, "9xx", 3) ==
nullptr);
EXPECT_TRUE(absl::strings_internal::memmatch(kHaystack, 10, "xxx", 1) ==
nullptr);
}
} }
} // namespace } // namespace
absl/strings/string_view.cc
...@@ -21,12 +21,35 @@ ...@@ -21,12 +21,35 @@
#include <cstring> #include <cstring>
#include <ostream> #include <ostream>
#include "absl/strings/internal/memutil.h"
namespace absl { namespace absl {
ABSL_NAMESPACE_BEGIN ABSL_NAMESPACE_BEGIN
namespace { namespace {
// This is significantly faster for case-sensitive matches with very
// few possible matches.
const char* memmatch(const char* phaystack, size_t haylen, const char* pneedle,
size_t neelen) {
if (0 == neelen) {
return phaystack; // even if haylen is 0
}
if (haylen < neelen) return nullptr;
const char* match;
const char* hayend = phaystack + haylen - neelen + 1;
// A static cast is used here to work around the fact that memchr returns
// a void* on Posix-compliant systems and const void* on Windows.
while (
(match = static_cast<const char*>(memchr(
phaystack, pneedle[0], static_cast<size_t>(hayend - phaystack))))) {
if (memcmp(match, pneedle, neelen) == 0)
return match;
else
phaystack = match + 1;
}
return nullptr;
}
void WritePadding(std::ostream& o, size_t pad) { void WritePadding(std::ostream& o, size_t pad) {
char fill_buf[32]; char fill_buf[32];
memset(fill_buf, o.fill(), sizeof(fill_buf)); memset(fill_buf, o.fill(), sizeof(fill_buf));
...@@ -84,8 +107,7 @@ string_view::size_type string_view::find(string_view s, ...@@ -84,8 +107,7 @@ string_view::size_type string_view::find(string_view s,
if (empty() && pos == 0 && s.empty()) return 0; if (empty() && pos == 0 && s.empty()) return 0;
return npos; return npos;
} }
const char* result = const char* result = memmatch(ptr_ + pos, length_ - pos, s.ptr_, s.length_);
strings_internal::memmatch(ptr_ + pos, length_ - pos, s.ptr_, s.length_);
return result ? static_cast<size_type>(result - ptr_) : npos; return result ? static_cast<size_type>(result - ptr_) : npos;
} }
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment