tiny.tldr.formats.elf.format.binary

1const std = @import("std");2const root = @import("../../root.zig");3const record = @import("record.zig");45const model = root.model;6const native_endian = record.native_endian;7const shdr_size = record.shdr_size;8const SectionHeader = record.SectionHeader;9const Symbol = record.Symbol;10const SymbolRecord = record.SymbolRecord;11const byte = @import("byte.zig");1213const copyInto = byte.copyInto;14const readU16 = byte.readU16;15const readU32 = byte.readU32;16const readU64 = byte.readU64;1718pub fn sectionBytes(bytes: []const u8, section: SectionHeader) model.Error![]const u8 {19    if (section.section_type == std.elf.SHT_NOBITS) return &.{};20    try requireRange(bytes, section.offset, section.size);21    const start: usize = @intCast(section.offset);22    const size: usize = @intCast(section.size);23    return bytes[start .. start + size];24}2526pub fn isElf(bytes: []const u8) bool {27    return bytes.len >= 4 and std.mem.eql(u8, bytes[0..4], std.elf.MAGIC);28}2930pub fn requireRange(bytes: []const u8, offset: u64, size: u64) model.Error!void {31    if (offset > bytes.len) return error.InvalidRange;32    if (size > bytes.len - offset) return error.InvalidRange;33}3435pub fn stringFromTable(table: []const u8, offset: u32) model.Error![]const u8 {36    if (offset >= table.len) return error.InvalidStringTable;37    const start: usize = @intCast(offset);38    const end = std.mem.indexOfScalarPos(u8, table, start, 0) orelse return error.InvalidStringTable;39    return table[start..end];40}4142pub fn decodeSectionHeaders(bytes: []const u8, shoff: u64, sections: []SectionHeader) void {43    if (native_endian == .little) {44        const start: usize = @intCast(shoff);45        const byte_count = sections.len * shdr_size;46        @memcpy(std.mem.sliceAsBytes(sections), bytes[start..][0..byte_count]);47        return;48    }4950    for (sections, 0..) |*section, index| {51        const offset: u64 = shoff + @as(u64, @intCast(index)) * shdr_size;52        section.* = readSectionHeader(bytes, offset);53    }54}5556pub fn readSectionHeader(bytes: []const u8, offset: u64) SectionHeader {57    const start: usize = @intCast(offset);58    return .{59        .name_offset = readU32(bytes[start..], 0),60        .section_type = readU32(bytes[start..], 4),61        .flags = readU64(bytes[start..], 8),62        .address = readU64(bytes[start..], 16),63        .offset = readU64(bytes[start..], 24),64        .size = readU64(bytes[start..], 32),65        .link = readU32(bytes[start..], 40),66        .info = readU32(bytes[start..], 44),67        .alignment = readU64(bytes[start..], 48),68        .entry_size = readU64(bytes[start..], 56),69    };70}7172/// Decodes one 24-byte ELF64 symbol table entry, stored little-endian, into its73/// on-disk record so the entry's byte layout is read in one place. The function74/// is the only decoder of that entry: `readSymbol` and `View.symbol` both call75/// it.76pub fn readSymbolRecord(bytes: []const u8) SymbolRecord {77    return .{78        .name_offset = readU32(bytes, 0),79        .info = bytes[4],80        .other = bytes[5],81        .section_index = readU16(bytes, 6),82        .value = readU64(bytes, 8),83        .size = readU64(bytes, 16),84    };85}8687/// Decodes one symbol table entry into the parsed symbol shape, by way of88/// `readSymbolRecord`. The object parser calls this function for each entry of89/// a symbol table before it resolves the names. The result's `name` is empty,90/// because the name lives in the symbol string table, which the caller holds91/// and looks up afterwards.92pub fn readSymbol(bytes: []const u8) Symbol {93    const wire = readSymbolRecord(bytes);94    return .{95        .name_offset = wire.name_offset,96        .info = wire.info,97        .other = wire.other,98        .section_index = wire.section_index,99        .value = wire.value,100        .size = wire.size,101    };102}103104pub fn validateAlignment(alignment: u64) model.Error!void {105    if (alignment == 0) return;106    if ((alignment & (alignment - 1)) != 0) return error.InvalidAlignment;107}108109pub fn alignForward(value: usize, alignment: usize) usize {110    if (alignment == 0) return value;111    const mask = alignment - 1;112    return (value + mask) & ~mask;113}114115pub fn alignForwardU64(value: u64, alignment: u64) u64 {116    if (alignment == 0) return value;117    const mask = alignment - 1;118    return (value + mask) & ~mask;119}

1pub const binary = @import("binary.zig");