[libc][Obvious] Some clean work with memmove.
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@ -28,30 +28,30 @@ static inline void move_byte_backward(char *dest_m, const char *src_m,
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}
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LLVM_LIBC_FUNCTION(void *, memmove,
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(void *dest, const void *src, size_t count)) {
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char *dest_c = reinterpret_cast<char *>(dest);
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(void *dst, const void *src, size_t count)) {
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char *dest_c = reinterpret_cast<char *>(dst);
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const char *src_c = reinterpret_cast<const char *>(src);
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// If the distance between src_c and dest_c is equal to or greater
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// than count (integerAbs(src_c - dest_c) >= count), they would not overlap.
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// If the distance between `src_c` and `dest_c` is equal to or greater
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// than `count` (integerAbs(src_c - dest_c) >= count), they would not overlap.
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// e.g. greater equal overlapping
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// [12345678] [12345678] [12345678]
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// src_c: [_ab_____] [_ab_____] [_ab_____]
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// dest_c:[_____yz_] [___yz___] [__yz____]
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// Use memcpy if src_c and dest_c do not overlap.
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// Call `memcpy` if `src_c` and `dest_c` do not overlap.
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if (__llvm_libc::integerAbs(src_c - dest_c) >= static_cast<ptrdiff_t>(count))
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return __llvm_libc::memcpy(dest_c, src_c, count);
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// Overlap cases.
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// If dest_c starts before src_c (dest_c < src_c), copy forward(pointer add 1)
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// from beginning to end.
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// If dest_c starts after src_c (dest_c > src_c), copy backward(pointer add
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// -1) from end to beginning.
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// If dest_c and src_c start at the same address (dest_c == src_c),
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// Overlapping cases.
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// If `dest_c` starts before `src_c` (dest_c < src_c), copy
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// forward(pointer add 1) from beginning to end.
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// If `dest_c` starts after `src_c` (dest_c > src_c), copy
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// backward(pointer add -1) from end to beginning.
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// If `dest_c` and `src_c` start at the same address (dest_c == src_c),
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// just return dest.
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// e.g. forward backward
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// *--> <--*
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// *-> <-*
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// src_c : [___abcde_] [_abcde___]
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// dest_c: [_abc--___] [___--cde_]
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@ -60,7 +60,7 @@ LLVM_LIBC_FUNCTION(void *, memmove,
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move_byte_forward(dest_c, src_c, count);
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if (dest_c > src_c)
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move_byte_backward(dest_c, src_c, count);
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return dest;
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return dst;
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}
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} // namespace __llvm_libc
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@ -13,7 +13,7 @@
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namespace __llvm_libc {
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void *memmove(void *dest, const void *src, size_t count);
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void *memmove(void *dst, const void *src, size_t count);
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} // namespace __llvm_libc
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@ -6,64 +6,65 @@
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//
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//===----------------------------------------------------------------------===//
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#include "src/string/memcmp.h"
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#include "src/string/memmove.h"
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#include "utils/CPP/ArrayRef.h"
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#include "utils/UnitTest/Test.h"
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class LlvmLibcMemmoveTest : public __llvm_libc::testing::Test {
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public:
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void check_memmove(void *dest, const void *src, size_t count, const void *str,
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void check_memmove(void *dst, const void *src, size_t count,
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const unsigned char *str,
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const __llvm_libc::cpp::ArrayRef<unsigned char> expected) {
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void *result = __llvm_libc::memmove(dest, src, count);
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// Making sure the pointer returned is same with dest.
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EXPECT_EQ(result, dest);
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// expected is designed according to str.
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// dest and src might be part of str.
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// Making sure the str is same with expected.
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EXPECT_EQ(__llvm_libc::memcmp(str, expected.data(), expected.size()), 0);
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void *result = __llvm_libc::memmove(dst, src, count);
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// Making sure the pointer returned is same with `dst`.
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EXPECT_EQ(result, dst);
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// `expected` is designed according to `str`.
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// `dst` and `src` might be part of `str`.
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// Making sure `str` is same with `expected`.
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for (size_t i = 0; i < expected.size(); ++i)
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EXPECT_EQ(str[i], expected[i]);
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}
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};
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TEST_F(LlvmLibcMemmoveTest, MoveZeroByte) {
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unsigned char dest[] = {'a', 'b'};
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unsigned char dst[] = {'a', 'b'};
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const unsigned char src[] = {'y', 'z'};
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const unsigned char expected[] = {'a', 'b'};
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check_memmove(dest, src, 0, dest, expected);
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check_memmove(dst, src, 0, dst, expected);
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}
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TEST_F(LlvmLibcMemmoveTest, OverlapThatDestAndSrcPointToSameAddress) {
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TEST_F(LlvmLibcMemmoveTest, OverlapThatDstAndSrcPointToSameAddress) {
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unsigned char str[] = {'a', 'b'};
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const unsigned char expected[] = {'a', 'b'};
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check_memmove(str, str, 1, str, expected);
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}
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TEST_F(LlvmLibcMemmoveTest, OverlapThatDestStartsBeforeSrc) {
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TEST_F(LlvmLibcMemmoveTest, OverlapThatDstStartsBeforeSrc) {
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// Set boundary at beginning and end for not overstepping when
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// copy forward or backward.
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unsigned char str[] = {'z', 'a', 'b', 'c', 'z'};
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const unsigned char expected[] = {'z', 'b', 'c', 'c', 'z'};
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// dest is &str[1].
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// `dst` is `&str[1]`.
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check_memmove(&str[1], &str[2], 2, str, expected);
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}
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TEST_F(LlvmLibcMemmoveTest, OverlapThatDestStartsAfterSrc) {
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TEST_F(LlvmLibcMemmoveTest, OverlapThatDstStartsAfterSrc) {
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unsigned char str[] = {'z', 'a', 'b', 'c', 'z'};
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const unsigned char expected[] = {'z', 'a', 'a', 'b', 'z'};
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check_memmove(&str[2], &str[1], 2, str, expected);
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}
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// e.g. dest follow src.
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// e.g. `dst` follow `src`.
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// str: [abcdefghij]
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// [__src_____]
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// [_____dest_]
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TEST_F(LlvmLibcMemmoveTest, SrcFollowDest) {
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// [_____dst__]
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TEST_F(LlvmLibcMemmoveTest, SrcFollowDst) {
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unsigned char str[] = {'z', 'a', 'b', 'z'};
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const unsigned char expected[] = {'z', 'b', 'b', 'z'};
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check_memmove(&str[1], &str[2], 1, str, expected);
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}
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TEST_F(LlvmLibcMemmoveTest, DestFollowSrc) {
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TEST_F(LlvmLibcMemmoveTest, DstFollowSrc) {
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unsigned char str[] = {'z', 'a', 'b', 'z'};
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const unsigned char expected[] = {'z', 'a', 'a', 'z'};
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check_memmove(&str[2], &str[1], 1, str, expected);
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