298 lines
6.6 KiB
V
298 lines
6.6 KiB
V
// Copyright (c) 2026 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
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// that can be found in the LICENSE file.
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module arm64
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// Mach-O Constants for ARM64
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const mh_magic_64 = u32(0xfeedfacf)
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const cpu_type_arm64 = 0x0100000c
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const cpu_subtype_arm64_all = 0
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const lc_segment_64 = 0x19
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const lc_symtab = 0x2
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const arm64_reloc_branch26 = 2
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const arm64_reloc_page21 = 3
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const arm64_reloc_pageoff12 = 4
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const arm64_reloc_got_load_page21 = 5
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const arm64_reloc_got_load_pageoff12 = 6
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pub struct MachOObject {
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pub mut:
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text_data []u8
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str_data []u8
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data_data []u8
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relocs []RelocationInfo
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symbols []Symbol
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str_table []u8
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sym_by_name map[string]int // symbol name → index in symbols
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}
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struct RelocationInfo {
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addr int
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sym_idx int
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pcrel bool
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length int
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extern bool
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type_ int
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}
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struct Symbol {
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mut:
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name string
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type_ u8
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sect u8
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desc u16
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value u64
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name_off int
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}
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pub fn MachOObject.new() &MachOObject {
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mut m := &MachOObject{
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text_data: []u8{}
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str_data: []u8{}
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data_data: []u8{}
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relocs: []RelocationInfo{}
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symbols: []Symbol{}
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str_table: [u8(0)]
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sym_by_name: map[string]int{}
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}
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return m
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}
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pub fn (mut m MachOObject) add_symbol(name string, addr u64, is_ext bool, sect u8) int {
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typ := if is_ext { u8(0x0f) } else { u8(0x0e) } // N_SECT | N_EXT : N_SECT
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// Check if symbol already exists (e.g., was added as undefined earlier)
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if i := m.sym_by_name[name] {
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mut s := &m.symbols[i]
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s.type_ = typ
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s.sect = sect
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s.value = addr
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return i
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}
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// Add new symbol
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idx := m.symbols.len
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name_off := m.str_table.len
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unsafe { m.str_table.push_many(name.str, name.len) }
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m.str_table << 0
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m.symbols << Symbol{
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name: name
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type_: typ
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sect: sect
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desc: 0
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value: addr
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name_off: name_off
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}
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m.sym_by_name[name] = idx
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return idx
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}
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pub fn (mut m MachOObject) add_undefined(name string) int {
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// Check for any existing symbol with this name (defined or undefined)
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if i := m.sym_by_name[name] {
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return i
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}
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idx := m.symbols.len
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name_off := m.str_table.len
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unsafe { m.str_table.push_many(name.str, name.len) }
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m.str_table << 0
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m.symbols << Symbol{
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name: name
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type_: 0x01 // N_UNDF | N_EXT
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sect: 0
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desc: 0
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value: 0
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name_off: name_off
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}
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m.sym_by_name[name] = idx
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return idx
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}
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pub fn (mut m MachOObject) add_reloc(addr int, sym_idx int, typ int, pcrel bool) {
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m.relocs << RelocationInfo{
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addr: addr
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sym_idx: sym_idx // 0-based symbol table index
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type_: typ
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pcrel: pcrel
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length: 2
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extern: true
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}
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}
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pub fn (mut m MachOObject) write(path string) {
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mut buf := []u8{}
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n_sects := 3
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header_size := 32
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seg_cmd_size := 72 + (80 * n_sects)
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symtab_cmd_size := 24
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load_cmds_size := seg_cmd_size + symtab_cmd_size
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text_off := header_size + load_cmds_size
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text_len := m.text_data.len
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cstring_off := text_off + text_len
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cstring_len := m.str_data.len
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data_off := cstring_off + cstring_len
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data_len := m.data_data.len
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reloc_off := data_off + data_len
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sym_off := reloc_off + (m.relocs.len * 8)
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sym_len := m.symbols.len * 16
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str_off := sym_off + sym_len
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str_size := m.str_table.len
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// 1. Header
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write_mh_magic_64(mut buf)
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write_u32_le(mut buf, u32(cpu_type_arm64))
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write_u32_le(mut buf, u32(cpu_subtype_arm64_all))
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write_u32_le(mut buf, 1) // MH_OBJECT
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write_u32_le(mut buf, 2) // ncmds
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write_u32_le(mut buf, u32(load_cmds_size))
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write_u32_le(mut buf, 0)
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write_u32_le(mut buf, 0)
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// 2. LC_SEGMENT_64
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write_u32_le(mut buf, u32(lc_segment_64))
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write_u32_le(mut buf, u32(seg_cmd_size))
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for _ in 0 .. 16 {
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buf << 0
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}
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write_u64_le(mut buf, 0)
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write_u64_le(mut buf, u64(text_len + cstring_len + data_len))
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write_u64_le(mut buf, u64(text_off))
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write_u64_le(mut buf, u64(text_len + cstring_len + data_len))
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write_u32_le(mut buf, 7)
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write_u32_le(mut buf, 7)
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write_u32_le(mut buf, u32(n_sects))
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write_u32_le(mut buf, 0)
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// Section 1: __text
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write_string_fixed(mut buf, '__text', 16)
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write_string_fixed(mut buf, '__TEXT', 16)
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write_u64_le(mut buf, 0) // Addr 0
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write_u64_le(mut buf, u64(text_len))
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write_u32_le(mut buf, u32(text_off))
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write_u32_le(mut buf, 4)
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write_u32_le(mut buf, u32(reloc_off))
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write_u32_le(mut buf, u32(m.relocs.len))
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write_u32_le(mut buf, u32(0x80000400))
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write_u32_le(mut buf, 0)
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write_u32_le(mut buf, 0)
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write_u32_le(mut buf, 0)
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// Section 2: __cstring
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write_string_fixed(mut buf, '__cstring', 16)
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write_string_fixed(mut buf, '__TEXT', 16)
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write_u64_le(mut buf, u64(text_len)) // Addr = text_len
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write_u64_le(mut buf, u64(cstring_len))
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write_u32_le(mut buf, u32(cstring_off))
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write_u32_le(mut buf, 0)
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write_u32_le(mut buf, 0)
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write_u32_le(mut buf, 0)
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write_u32_le(mut buf, 2) // S_CSTRING_LITERALS
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write_u32_le(mut buf, 0)
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write_u32_le(mut buf, 0)
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write_u32_le(mut buf, 0)
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// Section 3: __data
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write_string_fixed(mut buf, '__data', 16)
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write_string_fixed(mut buf, '__DATA', 16)
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write_u64_le(mut buf, u64(text_len + cstring_len)) // Addr = text_len + cstring_len
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write_u64_le(mut buf, u64(data_len))
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write_u32_le(mut buf, u32(data_off))
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write_u32_le(mut buf, 3) // align 8
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write_u32_le(mut buf, 0)
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write_u32_le(mut buf, 0)
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write_u32_le(mut buf, 0)
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write_u32_le(mut buf, 0)
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write_u32_le(mut buf, 0)
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write_u32_le(mut buf, 0)
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// 3. LC_SYMTAB
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write_u32_le(mut buf, u32(lc_symtab))
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write_u32_le(mut buf, u32(symtab_cmd_size))
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write_u32_le(mut buf, u32(sym_off))
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write_u32_le(mut buf, u32(m.symbols.len))
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write_u32_le(mut buf, u32(str_off))
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write_u32_le(mut buf, u32(str_size))
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buf << m.text_data
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buf << m.str_data
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buf << m.data_data
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for r in m.relocs {
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write_u32_le(mut buf, u32(r.addr))
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mut info := u32(r.sym_idx)
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if r.pcrel {
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info |= (1 << 24)
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}
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info |= (u32(r.length) << 25)
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if r.extern {
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info |= (1 << 27)
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}
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info |= (u32(r.type_) << 28)
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write_u32_le(mut buf, info)
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}
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for s in m.symbols {
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write_u32_le(mut buf, u32(s.name_off))
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buf << s.type_
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buf << s.sect
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write_u16_le(mut buf, s.desc)
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write_u64_le(mut buf, s.value)
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}
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buf << m.str_table
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if !write_file_array_raw(path, buf) {
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panic('failed to write Mach-O object')
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}
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}
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fn write_u32_le(mut b []u8, v u32) {
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b << u8(v)
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b << u8(v >> 8)
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b << u8(v >> 16)
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b << u8(v >> 24)
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}
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fn write_mh_magic_64(mut b []u8) {
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b << u8(0xcf)
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b << u8(0xfa)
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b << u8(0xed)
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b << u8(0xfe)
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}
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fn write_u64_le(mut b []u8, v u64) {
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b << u8(v)
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b << u8(v >> 8)
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b << u8(v >> 16)
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b << u8(v >> 24)
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b << u8(v >> 32)
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b << u8(v >> 40)
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b << u8(v >> 48)
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b << u8(v >> 56)
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}
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fn write_u16_le(mut b []u8, v u16) {
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b << u8(v)
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b << u8(v >> 8)
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}
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fn write_string_fixed(mut b []u8, s string, len int) {
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mut bytes := s.bytes()
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for bytes.len < len {
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bytes << 0
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}
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for i in 0 .. len {
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b << bytes[i]
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}
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}
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