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.

1 files changed, 31 insertions, 0 deletions

diff --git a/na/lib/string/arm/__aeabi_memset.s b/na/lib/string/arm/__aeabi_memset.s
new file mode 100644
index 0000000..f9f6058
--- /dev/null
+++ b/na/lib/string/arm/__aeabi_memset.s
@@ -0,0 +1,31 @@
+.syntax unified
+
+.global __aeabi_memclr8
+.global __aeabi_memclr4
+.global __aeabi_memclr
+.global __aeabi_memset8
+.global __aeabi_memset4
+.global __aeabi_memset
+
+.type __aeabi_memclr8,%function
+.type __aeabi_memclr4,%function
+.type __aeabi_memclr,%function
+.type __aeabi_memset8,%function
+.type __aeabi_memset4,%function
+.type __aeabi_memset,%function
+
+__aeabi_memclr8:
+__aeabi_memclr4:
+__aeabi_memclr:
+	movs  r2, #0
+__aeabi_memset8:
+__aeabi_memset4:
+__aeabi_memset:
+	cmp   r1, #0
+	beq   2f
+	adds  r1, r0, r1
+1:	strb  r2, [r0]
+	adds  r0, r0, #1
+	cmp   r1, r0
+	bne   1b
+2:	bx    lr