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src/CLI/Runtime/nub_string.s

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+.intel_syntax noprefix
+
+.equ SYS_MMAP, 9
+.equ SYS_MUNMAP, 11
+
+.text
+.globl nub_strlen
+# func nub_strlen(string: cstring): u64
+nub_strlen:
+    test rdi, rdi
+    jz null_string
+    xor rax, rax
+strlen_loop:
+    cmp byte ptr [rdi + rax], 0
+    je strlen_exit
+    inc rax
+    jmp strlen_loop
+null_string:
+    xor rax, rax
+strlen_exit:
+    ret
+
+.text
+.globl nub_cstring_to_string
+# func nub_cstring_to_string(string: cstring): []u8
+nub_cstring_to_string:
+    push rbx
+    push r12
+    push r13
+
+    mov rbx, rdi            # Save original pointer
+    call nub_strlen
+    mov r12, rax            # r12 = string length
+
+    # Calculate total space needed: 8 bytes (length) + string length
+    mov r13, r12
+    add r13, 8              # r13 = total bytes needed
+
+    # Round up to page size (4096 bytes) for mmap
+    add r13, 4095           # Add page_size - 1
+    and r13, -4096          # Align to page boundary
+
+    mov rax, SYS_MMAP
+    xor rdi, rdi            # addr = 0 (let kernel choose)
+    mov rsi, r13            # length = aligned size
+    mov rdx, 3              # prot = PROT_READ | PROT_WRITE
+    mov r10, 34             # flags = MAP_PRIVATE | MAP_ANONYMOUS (0x22)
+    mov r8, -1              # fd = -1
+    xor r9, r9              # offset = 0
+    syscall
+
+    # Check if mmap failed
+    cmp rax, -1
+    je mmap_failed
+
+    mov r13, rax            # r13 = pointer to mapped memory
+
+    # Store length at beginning of mapped memory
+    mov [r13], r12          # Store string length
+
+    # Copy string data if not empty
+    test r12, r12           # Check if length is 0
+    jz copy_done
+
+    lea rdi, [r13 + 8]
+    mov rsi, rbx
+    mov rcx, r12
+    call nub_memcpy
+
+copy_done:
+    mov rax, r13
+    jmp function_exit
+
+mmap_failed:
+    xor rax, rax
+
+function_exit:
+    pop r13
+    pop r12
+    pop rbx
+    ret
+
+.text
+.globl nub_string_free
+# func nub_string_free(string: []u8): void
+nub_string_free:
+    test rdi, rdi
+    jz free_exit
+
+    mov rsi, [rdi]
+    add rsi, 8
+
+    # Round up to page size
+    add rsi, 4095
+    and rsi, -4096
+
+    mov rax, SYS_MUNMAP
+    syscall
+free_exit:
+    ret