diff --git a/Makefile b/Makefile index c8fb67f..f3674a6 100644 --- a/Makefile +++ b/Makefile @@ -6,6 +6,7 @@ CXXFILES := acpi.cpp \ gdt.cpp \ idt.cpp \ keyboard.cpp \ + memmove.cpp \ memory.cpp \ multiboot.cpp \ pic.cpp \ diff --git a/kernel.cpp b/kernel.cpp index 0cb581f..26d5b7d 100644 --- a/kernel.cpp +++ b/kernel.cpp @@ -72,13 +72,3 @@ void kernel_main(void) } } -extern "C" -void memmove(char* dst, char* src, size_t sz) { - while (sz) { - *dst = *src; - ++dst; - ++src; - --sz; - } -} - diff --git a/memmove.cpp b/memmove.cpp new file mode 100644 index 0000000..06e37df --- /dev/null +++ b/memmove.cpp @@ -0,0 +1,78 @@ +/* Taken from newlib... */ + +#include +#include +#include + +/* Nonzero if either X or Y is not aligned on a "long" boundary. */ +#define UNALIGNED(X, Y) \ + (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1))) + +/* How many bytes are copied each iteration of the 4X unrolled loop. */ +#define BIGBLOCKSIZE (sizeof (long) << 2) + +/* How many bytes are copied each iteration of the word copy loop. */ +#define LITTLEBLOCKSIZE (sizeof (long)) + +/* Threshhold for punting to the byte copier. */ +#define TOO_SMALL(LEN) ((LEN) < BIGBLOCKSIZE) + +extern "C" +void *memmove (void *dst_void, const void *src_void, size_t length) +{ + char *dst = reinterpret_cast(dst_void); + const char *src = reinterpret_cast(src_void); + long *aligned_dst; + const long *aligned_src; + + if (src < dst && dst < src + length) + { + /* Destructive overlap...have to copy backwards */ + src += length; + dst += length; + while (length--) + { + *--dst = *--src; + } + } + else + { + /* Use optimizing algorithm for a non-destructive copy to closely + match memcpy. If the size is small or either SRC or DST is unaligned, + then punt into the byte copy loop. This should be rare. */ + if (!TOO_SMALL(length) && !UNALIGNED (src, dst)) + { + aligned_dst = (long*)dst; + aligned_src = (long*)src; + + /* Copy 4X long words at a time if possible. */ + while (length >= BIGBLOCKSIZE) + { + *aligned_dst++ = *aligned_src++; + *aligned_dst++ = *aligned_src++; + *aligned_dst++ = *aligned_src++; + *aligned_dst++ = *aligned_src++; + length -= BIGBLOCKSIZE; + } + + /* Copy one long word at a time if possible. */ + while (length >= LITTLEBLOCKSIZE) + { + *aligned_dst++ = *aligned_src++; + length -= LITTLEBLOCKSIZE; + } + + /* Pick up any residual with a byte copier. */ + dst = (char*)aligned_dst; + src = (char*)aligned_src; + } + + while (length--) + { + *dst++ = *src++; + } + } + + return dst_void; +} +