From 5278f6def4248391a481382bd7b0042b04c829f2 Mon Sep 17 00:00:00 2001
From: Richard Qin <richard.qin.x@gmail.com>
Date: Tue, 21 Apr 2026 23:16:50 +0800
Subject: feat: add string manipulation functions derived from musl libc

This commit introduces a variety of string manipulation functions, including:
- `memmem`: Searches for a substring in a memory area.
- `memmove`: Safely copies memory areas, handling overlaps.
- `mempcpy`: Copies memory and returns a pointer to the end of the destination.
- `memrchr`: Finds the last occurrence of a character in a memory area.
- `memset`: Fills a memory area with a specified value.
- `rindex`: Returns the last occurrence of a character in a string.
- `stpcpy` and `stpncpy`: Copies strings and returns a pointer to the end.
- `strcat`, `strchr`, `strcspn`, `strlcat`, `strlcpy`, `strlen`, `strncat`, `strncmp`, `strncpy`, `strnlen`, `strpbrk`, `strrchr`, `strstr`, `strtok`, and `strtok_r`: Various string manipulation functions for concatenation, searching, and tokenization.

Assembly implementations for `memcpy`, `memmove`, and `memset` are also included for optimized performance on x86_64 architectures.
---
 na/lib/string/i386/memcpy.s  | 32 +++++++++++++++++++
 na/lib/string/i386/memmove.s | 22 +++++++++++++
 na/lib/string/i386/memset.s  | 76 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 130 insertions(+)
 create mode 100644 na/lib/string/i386/memcpy.s
 create mode 100644 na/lib/string/i386/memmove.s
 create mode 100644 na/lib/string/i386/memset.s

(limited to 'na/lib/string/i386')

diff --git a/na/lib/string/i386/memcpy.s b/na/lib/string/i386/memcpy.s
new file mode 100644
index 0000000..0608dd8
--- /dev/null
+++ b/na/lib/string/i386/memcpy.s
@@ -0,0 +1,32 @@
+.global memcpy
+.global __memcpy_fwd
+.hidden __memcpy_fwd
+.type memcpy,@function
+memcpy:
+__memcpy_fwd:
+	push %esi
+	push %edi
+	mov 12(%esp),%edi
+	mov 16(%esp),%esi
+	mov 20(%esp),%ecx
+	mov %edi,%eax
+	cmp $4,%ecx
+	jc 1f
+	test $3,%edi
+	jz 1f
+2:	movsb
+	dec %ecx
+	test $3,%edi
+	jnz 2b
+1:	mov %ecx,%edx
+	shr $2,%ecx
+	rep
+	movsl
+	and $3,%edx
+	jz 1f
+2:	movsb
+	dec %edx
+	jnz 2b
+1:	pop %edi
+	pop %esi
+	ret
diff --git a/na/lib/string/i386/memmove.s b/na/lib/string/i386/memmove.s
new file mode 100644
index 0000000..2a6a504
--- /dev/null
+++ b/na/lib/string/i386/memmove.s
@@ -0,0 +1,22 @@
+.global memmove
+.type memmove,@function
+memmove:
+	mov 4(%esp),%eax
+	sub 8(%esp),%eax
+	cmp 12(%esp),%eax
+.hidden __memcpy_fwd
+	jae __memcpy_fwd
+	push %esi
+	push %edi
+	mov 12(%esp),%edi
+	mov 16(%esp),%esi
+	mov 20(%esp),%ecx
+	lea -1(%edi,%ecx),%edi
+	lea -1(%esi,%ecx),%esi
+	std
+	rep movsb
+	cld
+	lea 1(%edi),%eax
+	pop %edi
+	pop %esi
+	ret
diff --git a/na/lib/string/i386/memset.s b/na/lib/string/i386/memset.s
new file mode 100644
index 0000000..d00422c
--- /dev/null
+++ b/na/lib/string/i386/memset.s
@@ -0,0 +1,76 @@
+.global memset
+.type memset,@function
+memset:
+	mov 12(%esp),%ecx
+	cmp $62,%ecx
+	ja 2f
+
+	mov 8(%esp),%dl
+	mov 4(%esp),%eax
+	test %ecx,%ecx
+	jz 1f
+
+	mov %dl,%dh
+
+	mov %dl,(%eax)
+	mov %dl,-1(%eax,%ecx)
+	cmp $2,%ecx
+	jbe 1f
+
+	mov %dx,1(%eax)
+	mov %dx,(-1-2)(%eax,%ecx)
+	cmp $6,%ecx
+	jbe 1f
+
+	shl $16,%edx
+	mov 8(%esp),%dl
+	mov 8(%esp),%dh
+
+	mov %edx,(1+2)(%eax)
+	mov %edx,(-1-2-4)(%eax,%ecx)
+	cmp $14,%ecx
+	jbe 1f
+
+	mov %edx,(1+2+4)(%eax)
+	mov %edx,(1+2+4+4)(%eax)
+	mov %edx,(-1-2-4-8)(%eax,%ecx)
+	mov %edx,(-1-2-4-4)(%eax,%ecx)
+	cmp $30,%ecx
+	jbe 1f
+
+	mov %edx,(1+2+4+8)(%eax)
+	mov %edx,(1+2+4+8+4)(%eax)
+	mov %edx,(1+2+4+8+8)(%eax)
+	mov %edx,(1+2+4+8+12)(%eax)
+	mov %edx,(-1-2-4-8-16)(%eax,%ecx)
+	mov %edx,(-1-2-4-8-12)(%eax,%ecx)
+	mov %edx,(-1-2-4-8-8)(%eax,%ecx)
+	mov %edx,(-1-2-4-8-4)(%eax,%ecx)
+
+1:	ret 	
+
+2:	movzbl 8(%esp),%eax
+	mov %edi,12(%esp)
+	imul $0x1010101,%eax
+	mov 4(%esp),%edi
+	test $15,%edi
+	mov %eax,-4(%edi,%ecx)
+	jnz 2f
+
+1:	shr $2, %ecx
+	rep
+	stosl
+	mov 4(%esp),%eax
+	mov 12(%esp),%edi
+	ret
+	
+2:	xor %edx,%edx
+	sub %edi,%edx
+	and $15,%edx
+	mov %eax,(%edi)
+	mov %eax,4(%edi)
+	mov %eax,8(%edi)
+	mov %eax,12(%edi)
+	sub %edx,%ecx
+	add %edx,%edi
+	jmp 1b
-- 
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