Commit ed50bd1b65

Andrew Kelley <superjoe30@gmail.com>
2016-08-18 05:11:04
progress toward stack trace printing
1 parent 0fbb9e0
doc/style.md
@@ -62,7 +62,7 @@ const xml_document =
     \\<?xml version="1.0" encoding="UTF-8"?>
     \\<document>
     \\</document>
-    ;
+;
 struct XmlParser {}
 
 // The initials BE (Big Endian) are just another word in Zig identifier names.
example/cat/main.zig
@@ -14,7 +14,8 @@ pub fn main(args: [][]u8) -> %void {
         } else if (arg[0] == '-') {
             return usage(exe);
         } else {
-            var is = io.InStream.open(arg) %% |err| {
+            var is: io.InStream = undefined;
+            is.open(arg) %% |err| {
                 %%io.stderr.printf("Unable to open file: ");
                 %%io.stderr.printf(@errName(err));
                 %%io.stderr.printf("\n");
example/guess_number/main.zig
@@ -7,7 +7,7 @@ pub fn main(args: [][]u8) -> %void {
     %%io.stdout.printf("Welcome to the Guess Number Game in Zig.\n");
 
     var seed: [@sizeOf(usize)]u8 = undefined;
-    %%os.get_random_bytes(seed);
+    %%os.getRandomBytes(seed);
     var rand: Rand = undefined;
     rand.init(([]usize)(seed)[0]);
 
src/all_types.hpp
@@ -1232,6 +1232,7 @@ struct CodeGen {
         TypeTableEntry *entry_os_enum;
         TypeTableEntry *entry_arch_enum;
         TypeTableEntry *entry_environ_enum;
+        TypeTableEntry *entry_oformat_enum;
         TypeTableEntry *entry_atomic_order_enum;
     } builtin_types;
 
@@ -1256,6 +1257,7 @@ struct CodeGen {
     uint32_t target_os_index;
     uint32_t target_arch_index;
     uint32_t target_environ_index;
+    uint32_t target_oformat_index;
     LLVMTargetMachineRef target_machine;
     LLVMZigDIFile *dummy_di_file;
     bool is_native_target;
src/analyze.cpp
@@ -5296,6 +5296,9 @@ static TypeTableEntry *analyze_builtin_fn_call_expr(CodeGen *g, ImportTableEntry
                 } else if (buf_eql_str(var_name, "environ")) {
                     const_val->data.x_enum.tag = g->target_environ_index;
                     return g->builtin_types.entry_environ_enum;
+                } else if (buf_eql_str(var_name, "object_format")) {
+                    const_val->data.x_enum.tag = g->target_oformat_index;
+                    return g->builtin_types.entry_oformat_enum;
                 } else {
                     add_node_error(g, *str_node,
                         buf_sprintf("unrecognized compile variable: '%s'", buf_ptr(var_name)));
src/codegen.cpp
@@ -4576,6 +4576,33 @@ static void define_builtin_types(CodeGen *g) {
         g->builtin_types.entry_environ_enum = entry;
     }
 
+    {
+        TypeTableEntry *entry = new_type_table_entry(TypeTableEntryIdEnum);
+        entry->deep_const = true;
+        entry->zero_bits = true; // only allowed at compile time
+        buf_init_from_str(&entry->name, "@ObjectFormat");
+        uint32_t field_count = target_oformat_count();
+        entry->data.enumeration.field_count = field_count;
+        entry->data.enumeration.fields = allocate<TypeEnumField>(field_count);
+        for (uint32_t i = 0; i < field_count; i += 1) {
+            TypeEnumField *type_enum_field = &entry->data.enumeration.fields[i];
+            ZigLLVM_ObjectFormatType oformat = get_target_oformat(i);
+            type_enum_field->name = buf_create_from_str(get_target_oformat_name(oformat));
+            type_enum_field->value = i;
+            type_enum_field->type_entry = g->builtin_types.entry_void;
+
+            if (oformat == g->zig_target.oformat) {
+                g->target_oformat_index = i;
+            }
+        }
+        entry->data.enumeration.complete = true;
+
+        TypeTableEntry *tag_type_entry = get_smallest_unsigned_int_type(g, field_count);
+        entry->data.enumeration.tag_type = tag_type_entry;
+
+        g->builtin_types.entry_oformat_enum = entry;
+    }
+
     {
         TypeTableEntry *entry = new_type_table_entry(TypeTableEntryIdEnum);
         entry->deep_const = true;
src/target.cpp
@@ -137,6 +137,31 @@ static const ZigLLVM_EnvironmentType environ_list[] = {
     ZigLLVM_CoreCLR,
 };
 
+static const ZigLLVM_ObjectFormatType oformat_list[] = {
+    ZigLLVM_UnknownObjectFormat,
+    ZigLLVM_COFF,
+    ZigLLVM_ELF,
+    ZigLLVM_MachO,
+};
+
+int target_oformat_count(void) {
+    return array_length(oformat_list);
+}
+
+const ZigLLVM_ObjectFormatType get_target_oformat(int index) {
+    return oformat_list[index];
+}
+
+const char *get_target_oformat_name(ZigLLVM_ObjectFormatType oformat) {
+    switch (oformat) {
+        case ZigLLVM_UnknownObjectFormat: return "unknown";
+        case ZigLLVM_COFF: return "coff";
+        case ZigLLVM_ELF: return "elf";
+        case ZigLLVM_MachO: return "macho";
+    }
+    zig_unreachable();
+}
+
 int target_arch_count(void) {
     return array_length(arch_list);
 }
src/target.hpp
@@ -52,6 +52,11 @@ const char *get_target_os_name(ZigLLVM_OSType os_type);
 int target_environ_count(void);
 ZigLLVM_EnvironmentType get_target_environ(int index);
 
+
+int target_oformat_count(void);
+const ZigLLVM_ObjectFormatType get_target_oformat(int index);
+const char *get_target_oformat_name(ZigLLVM_ObjectFormatType oformat);
+
 void get_native_target(ZigTarget *target);
 void get_unknown_target(ZigTarget *target);
 
std/debug.zig
@@ -1,21 +1,123 @@
 const Allocator = @import("mem.zig").Allocator;
 const io = @import("io.zig");
+const os = @import("os.zig");
+const elf = @import("elf.zig");
+
+pub error MissingDebugInfo;
+pub error InvalidDebugInfo;
+pub error UnsupportedDebugInfo;
 
 pub fn assert(b: bool) {
     if (!b) unreachable{}
 }
 
-pub fn printStackTrace() {
-    var maybe_fp: ?&const u8 = @frameAddress();
-    while (true) {
-        const fp = maybe_fp ?? break;
-        const return_address = *(&const usize)(usize(fp) + @sizeOf(usize));
-        %%io.stderr.printInt(usize, return_address);
-        %%io.stderr.printf("\n");
-        maybe_fp = *(&const ?&const u8)(fp);
+pub fn printStackTrace() -> %void {
+    %return writeStackTrace(&io.stderr);
+    %return io.stderr.flush();
+}
+
+pub fn writeStackTrace(out_stream: &io.OutStream) -> %void {
+    switch (@compileVar("object_format")) {
+        elf => {
+            var st: ElfStackTrace = undefined;
+            %return io.openSelfExe(&st.self_exe_stream);
+            defer %return st.self_exe_stream.close();
+
+            %return st.elf.openStream(&global_allocator, &st.self_exe_stream);
+            defer %return st.elf.close();
+
+            st.aranges = %return st.elf.findSection(".debug_aranges");
+
+            var maybe_fp: ?&const u8 = @frameAddress();
+            while (true) {
+                const fp = maybe_fp ?? break;
+                const return_address = *(&const usize)(usize(fp) + @sizeOf(usize));
+
+                // read .debug_aranges to find out which compile unit the address is in
+                const debug_info_offset = %return debugInfoOffset(&st, return_address);
+
+                %return out_stream.printInt(usize, return_address);
+                %return out_stream.printf("  -> ");
+                %return out_stream.printInt(u64, debug_info_offset);
+                %return out_stream.printf("\n");
+                maybe_fp = *(&const ?&const u8)(fp);
+            }
+        },
+        coff => {
+            out_stream.write("(stack trace unavailable for COFF object format)\n");
+        },
+        macho => {
+            out_stream.write("(stack trace unavailable for Mach-O object format)\n");
+        },
+        unknown => {
+            out_stream.write("(stack trace unavailable for unknown object format)\n");
+        },
     }
 }
 
+struct ElfStackTrace {
+    self_exe_stream: io.InStream,
+    elf: elf.Elf,
+    aranges: ?&elf.SectionHeader,
+}
+
+fn debugInfoOffset(st: &ElfStackTrace, target_address: usize) -> %u64 {
+    // when there is no .debug_aranges section, offset into debug info is 0x0
+    const aranges = st.aranges ?? return 0;
+
+    %return st.elf.seekToSection(aranges);
+
+    const first_32_bits = %return st.self_exe_stream.readIntLe(u32);
+    const is_64 = (first_32_bits == 0xffffffff);
+    const unit_length = if (is_64) {
+        %return st.self_exe_stream.readIntLe(u64)
+    } else {
+        if (first_32_bits >= 0xfffffff0) return error.InvalidDebugInfo;
+        first_32_bits
+    };
+    var unit_index: u64 = 0;
+
+    while (unit_index < unit_length) {
+        const version = %return st.self_exe_stream.readIntLe(u16);
+        if (version != 2) return error.InvalidDebugInfo;
+        unit_index += 2;
+
+        const debug_info_offset = if (is_64) {
+            unit_index += 4;
+            %return st.self_exe_stream.readIntLe(u64)
+        } else {
+            unit_index += 2;
+            %return st.self_exe_stream.readIntLe(u32)
+        };
+
+        const address_size = %return st.self_exe_stream.readByte();
+        if (address_size > 8) return error.UnsupportedDebugInfo;
+        unit_index += 1;
+
+        const segment_size = %return st.self_exe_stream.readByte();
+        if (segment_size > 0) return error.UnsupportedDebugInfo;
+        unit_index += 1;
+
+        const align = segment_size + 2 * address_size;
+        const padding = st.self_exe_stream.offset % align;
+        %return st.self_exe_stream.seekForward(padding);
+        unit_index += padding;
+
+        while (true) {
+            const address = %return st.self_exe_stream.readVarInt(false, u64, address_size);
+            const length = %return st.self_exe_stream.readVarInt(false, u64, address_size);
+            unit_index += align;
+            if (address == 0 && length == 0) break;
+
+            if (target_address >= address && target_address < address + length) {
+                return debug_info_offset;
+            }
+        }
+    }
+
+    return error.MissingDebugInfo;
+}
+
 pub var global_allocator = Allocator {
     .allocFn = globalAlloc,
     .reallocFn = globalRealloc,
std/elf.zig
@@ -0,0 +1,261 @@
+const io = @import("io.zig");
+const str = @import("str.zig");
+const math = @import("math.zig");
+const mem = @import("mem.zig");
+const debug = @import("debug.zig");
+
+pub error InvalidFormat;
+
+pub const SHT_NULL = 0;
+pub const SHT_PROGBITS = 1;
+pub const SHT_SYMTAB = 2;
+pub const SHT_STRTAB = 3;
+pub const SHT_RELA = 4;
+pub const SHT_HASH = 5;
+pub const SHT_DYNAMIC = 6;
+pub const SHT_NOTE = 7;
+pub const SHT_NOBITS = 8;
+pub const SHT_REL = 9;
+pub const SHT_SHLIB = 10;
+pub const SHT_DYNSYM = 11;
+pub const SHT_INIT_ARRAY = 14;
+pub const SHT_FINI_ARRAY = 15;
+pub const SHT_PREINIT_ARRAY = 16;
+pub const SHT_GROUP = 17;
+pub const SHT_SYMTAB_SHNDX = 18;
+pub const SHT_LOOS = 0x60000000;
+pub const SHT_HIOS = 0x6fffffff;
+pub const SHT_LOPROC = 0x70000000;
+pub const SHT_HIPROC = 0x7fffffff;
+pub const SHT_LOUSER = 0x80000000;
+pub const SHT_HIUSER = 0xffffffff;
+
+pub enum FileType {
+    Relocatable,
+    Executable,
+    Shared,
+    Core,
+}
+
+pub enum Arch {
+    Sparc,
+    x86,
+    Mips,
+    PowerPc,
+    Arm,
+    SuperH,
+    IA_64,
+    x86_64,
+    AArch64,
+}
+
+pub struct SectionHeader {
+    name: u32,
+    sh_type: u32,
+    flags: u64,
+    addr: u64,
+    offset: u64,
+    size: u64,
+    link: u32,
+    info: u32,
+    addr_align: u64,
+    ent_size: u64,
+}
+
+pub struct Elf {
+    in_stream: &io.InStream,
+    auto_close_stream: bool,
+    is_64: bool,
+    is_big_endian: bool,
+    file_type: FileType,
+    arch: Arch,
+    entry_addr: u64,
+    program_header_offset: u64,
+    section_header_offset: u64,
+    string_section_index: u64,
+    string_section: &SectionHeader,
+    section_headers: []SectionHeader,
+    allocator: &mem.Allocator,
+    prealloc_stream: io.InStream,
+
+    /// Call close when done.
+    pub fn openFile(elf: &Elf, allocator: &mem.Allocator, path: []const u8) -> %void {
+        %return elf.prealloc_stream.open(path);
+        %return elf.openStream(allocator, &elf.prealloc_stream);
+        elf.auto_close_stream = true;
+    }
+
+    /// Call close when done.
+    pub fn openStream(elf: &Elf, allocator: &mem.Allocator, stream: &io.InStream) -> %void {
+        elf.allocator = allocator;
+        elf.in_stream = stream;
+        elf.auto_close_stream = false;
+
+        var magic: [4]u8 = undefined;
+        %return elf.in_stream.readNoEof(magic);
+        if (!str.eql(magic, "\x7fELF")) return error.InvalidFormat;
+
+        elf.is_64 = switch (%return elf.in_stream.readByte()) {
+            1 => false,
+            2 => true,
+            else => return error.InvalidFormat,
+        };
+
+        elf.is_big_endian = switch (%return elf.in_stream.readByte()) {
+            1 => false,
+            2 => true,
+            else => return error.InvalidFormat,
+        };
+
+        const version_byte = %return elf.in_stream.readByte();
+        if (version_byte != 1) return error.InvalidFormat;
+
+        // skip over padding
+        %return elf.in_stream.seekForward(9);
+
+        elf.file_type = switch (%return elf.in_stream.readInt(elf.is_big_endian, u16)) {
+            1 => FileType.Relocatable,
+            2 => FileType.Executable,
+            3 => FileType.Shared,
+            4 => FileType.Core,
+            else => return error.InvalidFormat,
+        };
+
+        elf.arch = switch (%return elf.in_stream.readInt(elf.is_big_endian, u16)) {
+            0x02 => Arch.Sparc,
+            0x03 => Arch.x86,
+            0x08 => Arch.Mips,
+            0x14 => Arch.PowerPc,
+            0x28 => Arch.Arm,
+            0x2A => Arch.SuperH,
+            0x32 => Arch.IA_64,
+            0x3E => Arch.x86_64,
+            0xb7 => Arch.AArch64,
+            else => return error.InvalidFormat,
+        };
+
+        const elf_version = %return elf.in_stream.readInt(elf.is_big_endian, u32);
+        if (elf_version != 1) return error.InvalidFormat;
+
+        if (elf.is_64) {
+            elf.entry_addr = %return elf.in_stream.readInt(elf.is_big_endian, u64);
+            elf.program_header_offset = %return elf.in_stream.readInt(elf.is_big_endian, u64);
+            elf.section_header_offset = %return elf.in_stream.readInt(elf.is_big_endian, u64);
+        } else {
+            elf.entry_addr = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
+            elf.program_header_offset = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
+            elf.section_header_offset = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
+        }
+
+        // skip over flags
+        %return elf.in_stream.seekForward(4);
+
+        const header_size = %return elf.in_stream.readInt(elf.is_big_endian, u16);
+        if ((elf.is_64 && header_size != 64) ||
+            (!elf.is_64 && header_size != 52))
+        {
+            return error.InvalidFormat;
+        }
+
+        const ph_entry_size = %return elf.in_stream.readInt(elf.is_big_endian, u16);
+        const ph_entry_count = %return elf.in_stream.readInt(elf.is_big_endian, u16);
+        const sh_entry_size = %return elf.in_stream.readInt(elf.is_big_endian, u16);
+        const sh_entry_count = %return elf.in_stream.readInt(elf.is_big_endian, u16);
+        elf.string_section_index = u64(%return elf.in_stream.readInt(elf.is_big_endian, u16));
+
+        if (elf.string_section_index >= sh_entry_count) return error.InvalidFormat;
+
+        const sh_byte_count = u64(sh_entry_size) * u64(sh_entry_count);
+        const end_sh = %return math.addOverflow(u64, elf.section_header_offset, sh_byte_count);
+        const ph_byte_count = u64(ph_entry_size) * u64(ph_entry_count);
+        const end_ph = %return math.addOverflow(u64, elf.program_header_offset, ph_byte_count);
+
+        const stream_end = %return elf.in_stream.endPos();
+        if (stream_end < end_sh || stream_end < end_ph) {
+            return error.InvalidFormat;
+        }
+
+        %return elf.in_stream.seekTo(elf.section_header_offset);
+
+        elf.section_headers = %return elf.allocator.alloc(SectionHeader, sh_entry_count);
+        %defer elf.allocator.free(SectionHeader, elf.section_headers);
+
+        if (elf.is_64) {
+            if (sh_entry_size != 64) return error.InvalidFormat;
+
+            for (elf.section_headers) |*section| {
+                section.name         = %return elf.in_stream.readInt(elf.is_big_endian, u32);
+                section.sh_type      = %return elf.in_stream.readInt(elf.is_big_endian, u32);
+                section.flags        = %return elf.in_stream.readInt(elf.is_big_endian, u64);
+                section.addr         = %return elf.in_stream.readInt(elf.is_big_endian, u64);
+                section.offset       = %return elf.in_stream.readInt(elf.is_big_endian, u64);
+                section.size         = %return elf.in_stream.readInt(elf.is_big_endian, u64);
+                section.link         = %return elf.in_stream.readInt(elf.is_big_endian, u32);
+                section.info         = %return elf.in_stream.readInt(elf.is_big_endian, u32);
+                section.addr_align   = %return elf.in_stream.readInt(elf.is_big_endian, u64);
+                section.ent_size     = %return elf.in_stream.readInt(elf.is_big_endian, u64);
+            }
+        } else {
+            if (sh_entry_size != 40) return error.InvalidFormat;
+
+            for (elf.section_headers) |*section| {
+                // TODO (multiple occurences) allow implicit cast from %u32 -> %u64 ?
+                section.name = %return elf.in_stream.readInt(elf.is_big_endian, u32);
+                section.sh_type = %return elf.in_stream.readInt(elf.is_big_endian, u32);
+                section.flags = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
+                section.addr = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
+                section.offset = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
+                section.size = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
+                section.link = %return elf.in_stream.readInt(elf.is_big_endian, u32);
+                section.info = %return elf.in_stream.readInt(elf.is_big_endian, u32);
+                section.addr_align = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
+                section.ent_size = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
+            }
+        }
+
+        for (elf.section_headers) |*section| {
+            if (section.sh_type != SHT_NOBITS) {
+                const file_end_offset = %return math.addOverflow(u64,
+                    section.offset, section.size);
+                if (stream_end < file_end_offset) return error.InvalidFormat;
+            }
+        }
+
+        elf.string_section = &elf.section_headers[elf.string_section_index];
+        if (elf.string_section.sh_type != SHT_STRTAB) {
+            // not a string table
+            return error.InvalidFormat;
+        }
+    }
+
+    pub fn close(elf: &Elf) -> %void {
+        elf.allocator.free(SectionHeader, elf.section_headers);
+        if (elf.auto_close_stream) %return elf.in_stream.close();
+    }
+
+    pub fn findSection(elf: &Elf, name: []u8) -> %?&SectionHeader {
+        for (elf.section_headers) |*section| {
+            if (section.sh_type == SHT_NULL) continue;
+
+            const name_offset = elf.string_section.offset + section.name;
+            %return elf.in_stream.seekTo(name_offset);
+
+            for (name) |expected_c| {
+                const target_c = %return elf.in_stream.readByte();
+                if (target_c == 0 || expected_c != target_c) goto next_section;
+            }
+
+            const null_byte = %return elf.in_stream.readByte();
+            if (null_byte == 0) return (?&SectionHeader)(section);
+
+            next_section:
+        }
+
+        const null_sh: ?&SectionHeader = null;
+        return null_sh;
+    }
+
+    pub fn seekToSection(elf: &Elf, section: &SectionHeader) -> %void {
+        %return elf.in_stream.seekTo(section.offset);
+    }
+}
std/endian.zig
@@ -0,0 +1,21 @@
+pub inline fn swapIfLe(inline T: type, x: T) -> T {
+    swapIf(false, T, x)
+}
+
+pub inline fn swapIfBe(inline T: type, x: T) -> T {
+    swapIf(true, T, x)
+}
+
+pub inline fn swapIf(is_be: bool, inline T: type, x: T) -> T {
+    if (@compileVar("is_big_endian") == is_be) swap(T, x) else x
+}
+
+pub fn swap(inline T: type, x: T) -> T {
+    const x_slice = ([]u8)((&const x)[0...1]);
+    var result: T = undefined;
+    const result_slice = ([]u8)((&result)[0...1]);
+    for (result_slice) |*b, i| {
+        *b = x_slice[@sizeOf(T) - i - 1];
+    }
+    return result;
+}
std/io.zig
@@ -1,6 +1,9 @@
 const linux = @import("linux.zig");
 const errno = @import("errno.zig");
 const math = @import("math.zig");
+const endian = @import("endian.zig");
+const debug = @import("debug.zig");
+const assert = debug.assert;
 
 pub const stdin_fileno = 0;
 pub const stdout_fileno = 1;
@@ -8,6 +11,7 @@ pub const stderr_fileno = 2;
 
 pub var stdin = InStream {
     .fd = stdin_fileno,
+    .offset = 0,
 };
 
 pub var stdout = OutStream {
@@ -33,6 +37,8 @@ pub error Unexpected;
 
 pub error DiskQuota;
 pub error FileTooBig;
+// TODO hide interrupts at this layer by retrying. Users can use the linux specific APIs if they
+// want to handle interrupts.
 pub error SigInterrupt;
 pub error Io;
 pub error NoSpaceLeft;
@@ -48,6 +54,8 @@ pub error NameTooLong;
 pub error NoDevice;
 pub error PathNotFound;
 pub error NoMem;
+pub error Unseekable;
+pub error Eof;
 
 const buffer_size = 4 * 1024;
 const max_u64_base10_digits = 20;
@@ -137,14 +145,18 @@ pub struct OutStream {
     }
 }
 
+// TODO created a BufferedInStream struct and move some of this code there
+// BufferedInStream API goes on top of minimal InStream API.
 pub struct InStream {
     fd: i32,
-
-    pub fn open(path: []u8) -> %InStream {
-        const fd = linux.open(path, linux.O_LARGEFILE|linux.O_RDONLY, 0);
-        const fd_err = linux.getErrno(fd);
-        if (fd_err > 0) {
-            return switch (fd_err) {
+    offset: usize,
+
+    /// Call close to clean up.
+    pub fn open(is: &InStream, path: []const u8) -> %void {
+        const result = linux.open(path, linux.O_LARGEFILE|linux.O_RDONLY, 0);
+        const err = linux.getErrno(result);
+        if (err > 0) {
+            return switch (err) {
                 errno.EFAULT => unreachable{},
                 errno.EINVAL => unreachable{},
                 errno.EACCES => error.BadPerm,
@@ -164,24 +176,8 @@ pub struct InStream {
                 else => error.Unexpected,
             }
         }
-
-        return InStream { .fd = i32(fd), };
-    }
-
-    pub fn read(is: &InStream, buf: []u8) -> %usize {
-        const amt_read = linux.read(is.fd, &buf[0], buf.len);
-        const read_err = linux.getErrno(amt_read);
-        if (read_err > 0) {
-            return switch (read_err) {
-                errno.EINVAL => unreachable{},
-                errno.EFAULT => unreachable{},
-                errno.EBADF  => error.BadFd,
-                errno.EINTR  => error.SigInterrupt,
-                errno.EIO    => error.Io,
-                else         => error.Unexpected,
-            }
-        }
-        return amt_read;
+        is.fd = i32(result);
+        is.offset = 0;
     }
 
     pub fn close(is: &InStream) -> %void {
@@ -196,6 +192,95 @@ pub struct InStream {
             }
         }
     }
+
+    /// Returns the number of bytes read. If the number read is smaller than buf.len, then
+    /// the stream reached End Of File.
+    pub fn read(is: &InStream, buf: []u8) -> %usize {
+        switch (@compileVar("os")) {
+            linux => {
+                while (true) {
+                    const amt_read = linux.pread(is.fd, buf.ptr, buf.len, is.offset);
+                    const read_err = linux.getErrno(amt_read);
+                    if (read_err > 0) {
+                        switch (read_err) {
+                            errno.EINTR  => continue,
+                            errno.EINVAL => unreachable{},
+                            errno.EFAULT => unreachable{},
+                            errno.EBADF  => return error.BadFd,
+                            errno.EIO    => return error.Io,
+                            else         => return error.Unexpected,
+                        }
+                    }
+                    is.offset += amt_read;
+                    return amt_read;
+                }
+            },
+            else => @compileErr("unsupported OS"),
+        }
+    }
+
+    pub fn readNoEof(is: &InStream, buf: []u8) -> %void {
+        const amt_read = %return is.read(buf);
+        if (amt_read < buf.len) return error.Eof;
+    }
+
+    pub fn readByte(is: &InStream) -> %u8 {
+        var result: [1]u8 = undefined;
+        %return is.readNoEof(result);
+        return result[0];
+    }
+
+    pub inline fn readIntLe(is: &InStream, inline T: type) -> %T {
+        is.readInt(false, T)
+    }
+
+    pub inline fn readIntBe(is: &InStream, inline T: type) -> %T {
+        is.readInt(true, T)
+    }
+
+    pub inline fn readInt(is: &InStream, is_be: bool, inline T: type) -> %T {
+        var result: T = undefined;
+        const result_slice = ([]u8)((&result)[0...1]);
+        %return is.readNoEof(result_slice);
+        return endian.swapIf(!is_be, T, result);
+    }
+
+    pub inline fn readVarInt(is: &InStream, is_be: bool, inline T: type, size: usize) -> %T {
+        var result: T = zeroes;
+        const result_slice = ([]u8)((&result)[0...1]);
+        const padding = @sizeOf(T) - size;
+        {var i: usize = 0; while (i < size; i += 1) {
+            const index = if (is_be == @compileVar("is_big_endian")) {
+                padding + i
+            } else {
+                result_slice.len - i - 1 - padding
+            };
+            result_slice[index] = %return is.readByte();
+        }}
+        return result;
+    }
+
+    pub fn seekForward(is: &InStream, amount: usize) -> %void {
+        is.offset += amount;
+    }
+
+    pub fn seekTo(is: &InStream, pos: usize) -> %void {
+        is.offset = pos;
+    }
+
+    pub fn endPos(is: &InStream) -> %usize {
+        var stat: linux.stat = undefined;
+        const err = linux.getErrno(linux.fstat(is.fd, &stat));
+        if (err > 0) {
+            return switch (err) {
+                errno.EBADF => error.BadFd,
+                errno.ENOMEM => error.NoMem,
+                else => error.Unexpected,
+            }
+        }
+
+        return usize(stat.size);
+    }
 }
 
 pub fn parseUnsigned(inline T: type, buf: []u8, radix: u8) -> %T {
@@ -267,3 +352,12 @@ fn parseU64DigitTooBig() {
     };
     unreachable{};
 }
+
+pub fn openSelfExe(stream: &InStream) -> %void {
+    switch (@compileVar("os")) {
+        linux => {
+            %return stream.open("/proc/self/exe");
+        },
+        else => @compileErr("unsupported os"),
+    }
+}
std/linux.zig
@@ -76,6 +76,10 @@ pub const O_PATH = arch.O_PATH;
 pub const O_TMPFILE = arch.O_TMPFILE;
 pub const O_NDELAY = arch.O_NDELAY;
 
+pub const SEEK_SET = 0;
+pub const SEEK_CUR = 1;
+pub const SEEK_END = 2;
+
 const SIG_BLOCK   = 0;
 const SIG_UNBLOCK = 1;
 const SIG_SETMASK = 2;
@@ -226,7 +230,9 @@ pub fn getErrno(r: usize) -> usize {
     if (signed_r > -4096 && signed_r < 0) usize(-signed_r) else 0
 }
 
-pub fn mmap(address: ?&u8, length: usize, prot: usize, flags: usize, fd: i32, offset: usize) -> usize {
+pub fn mmap(address: ?&u8, length: usize, prot: usize, flags: usize, fd: i32, offset: usize)
+    -> usize
+{
     arch.syscall6(arch.SYS_mmap, usize(address), length, prot, flags, usize(fd), offset)
 }
 
@@ -238,29 +244,49 @@ pub fn read(fd: i32, buf: &u8, count: usize) -> usize {
     arch.syscall3(arch.SYS_read, usize(fd), usize(buf), count)
 }
 
+pub fn pread(fd: i32, buf: &u8, count: usize, offset: usize) -> usize {
+    arch.syscall4(arch.SYS_pread, usize(fd), usize(buf), count, offset)
+}
+
 pub fn write(fd: i32, buf: &const u8, count: usize) -> usize {
     arch.syscall3(arch.SYS_write, usize(fd), usize(buf), count)
 }
 
-pub fn open(path: []u8, flags: usize, perm: usize) -> usize {
+pub fn pwrite(fd: i32, buf: &const u8, count: usize, offset: usize) -> usize {
+    arch.syscall4(arch.SYS_pwrite, usize(fd), usize(buf), count, offset)
+}
+
+pub fn open_c(path: &const u8, flags: usize, perm: usize) -> usize {
+    arch.syscall3(arch.SYS_open, usize(path), flags, perm)
+}
+
+pub fn open(path: []const u8, flags: usize, perm: usize) -> usize {
     var buf: [path.len + 1]u8 = undefined;
     @memcpy(&buf[0], &path[0], path.len);
     buf[path.len] = 0;
-    arch.syscall3(arch.SYS_open, usize(&buf[0]), flags, perm)
+    return open_c(buf.ptr, flags, perm);
 }
 
-pub fn create(path: []u8, perm: usize) -> usize {
+pub fn create_c(path: &const u8, perm: usize) -> usize {
+    arch.syscall2(arch.SYS_creat, usize(path), perm)
+}
+
+pub fn create(path: []const u8, perm: usize) -> usize {
     var buf: [path.len + 1]u8 = undefined;
     @memcpy(&buf[0], &path[0], path.len);
     buf[path.len] = 0;
-    arch.syscall2(arch.SYS_creat, usize(&buf[0]), perm)
+    return create_c(buf.ptr, perm);
+}
+
+pub fn openat_c(dirfd: i32, path: &const u8, flags: usize, mode: usize) -> usize {
+    arch.syscall4(arch.SYS_openat, usize(dirfd), usize(path), flags, mode)
 }
 
-pub fn openat(dirfd: i32, path: []u8, flags: usize, mode: usize) -> usize {
+pub fn openat(dirfd: i32, path: []const u8, flags: usize, mode: usize) -> usize {
     var buf: [path.len + 1]u8 = undefined;
     @memcpy(&buf[0], &path[0], path.len);
     buf[path.len] = 0;
-    arch.syscall4(arch.SYS_openat, usize(dirfd), usize(&buf[0]), flags, mode)
+    return openat_c(dirfd, buf.ptr, flags, mode);
 }
 
 pub fn close(fd: i32) -> usize {
@@ -457,3 +483,10 @@ pub fn accept4(fd: i32, noalias addr: &sockaddr, noalias len: &socklen_t, flags:
 //     }
 //     return ifr.ifr_ifindex;
 // }
+
+pub const stat = arch.stat;
+pub const timespec = arch.timespec;
+
+pub fn fstat(fd: i32, stat_buf: &stat) -> usize {
+    arch.syscall2(arch.SYS_fstat, usize(fd), usize(stat_buf))
+}
std/linux_x86_64.zig
@@ -19,8 +19,8 @@ pub const SYS_rt_sigaction = 13;
 pub const SYS_rt_sigprocmask = 14;
 pub const SYS_rt_sigreturn = 15;
 pub const SYS_ioctl = 16;
-pub const SYS_pread64 = 17;
-pub const SYS_pwrite64 = 18;
+pub const SYS_pread = 17;
+pub const SYS_pwrite = 18;
 pub const SYS_readv = 19;
 pub const SYS_writev = 20;
 pub const SYS_access = 21;
@@ -453,3 +453,28 @@ export struct msghdr {
     __pad2: socklen_t,
     msg_flags: i32,
 }
+
+export struct stat {
+    dev: u64,
+    ino: u64,
+    nlink: usize,
+
+    mode: u32,
+    uid: u32,
+    gid: u32,
+    __pad0: u32,
+    rdev: u64,
+    size: i64,
+    blksize: isize,
+    blocks: i64,
+
+    atim: timespec,
+    mtim: timespec,
+    ctim: timespec,
+    __unused: [3]isize,
+}
+
+export struct timespec {
+    tv_sec: isize,
+    tv_nsec: isize,
+}
std/net.zig
@@ -1,6 +1,7 @@
 const linux = @import("linux.zig");
 const errno = @import("errno.zig");
 const assert = @import("debug.zig").assert;
+const endian = @import("endian.zig");
 
 pub error SigInterrupt;
 pub error Unexpected;
@@ -99,14 +100,14 @@ pub fn connectAddr(addr: &Address, port: u16) -> %Connection {
     const connect_ret = if (addr.family == linux.AF_INET) {
         var os_addr: linux.sockaddr_in = undefined;
         os_addr.family = addr.family;
-        os_addr.port = swapIfLittleEndian(u16, port);
+        os_addr.port = endian.swapIfLe(u16, port);
         @memcpy((&u8)(&os_addr.addr), &addr.addr[0], 4);
         @memset(&os_addr.zero, 0, @sizeOf(@typeOf(os_addr.zero)));
         linux.connect(socket_fd, (&linux.sockaddr)(&os_addr), @sizeOf(linux.sockaddr_in))
     } else if (addr.family == linux.AF_INET6) {
         var os_addr: linux.sockaddr_in6 = undefined;
         os_addr.family = addr.family;
-        os_addr.port = swapIfLittleEndian(u16, port);
+        os_addr.port = endian.swapIfLe(u16, port);
         os_addr.flowinfo = 0;
         os_addr.scope_id = addr.scope_id;
         @memcpy(&os_addr.addr[0], &addr.addr[0], 16);
@@ -319,7 +320,7 @@ fn parseIp4(buf: []const u8) -> %u32 {
 
 #attribute("test")
 fn testParseIp4() {
-    assert(%%parseIp4("127.0.0.1") == swapIfLittleEndian(u32, 0x7f000001));
+    assert(%%parseIp4("127.0.0.1") == endian.swapIfLe(u32, 0x7f000001));
     switch (parseIp4("256.0.0.1")) { Overflow => {}, else => unreachable {}, }
     switch (parseIp4("x.0.0.1")) { InvalidChar => {}, else => unreachable {}, }
     switch (parseIp4("127.0.0.1.1")) { JunkAtEnd => {}, else => unreachable {}, }
@@ -351,17 +352,3 @@ fn testLookupSimpleIp() {
         assert(addr.addr[3] == 1);
     }
 }
-
-fn swapIfLittleEndian(inline T: type, x: T) -> T {
-    if (@compileVar("is_big_endian")) x else endianSwap(T, x)
-}
-
-fn endianSwap(inline T: type, x: T) -> T {
-    const x_slice = ([]u8)((&const x)[0...1]);
-    var result: T = undefined;
-    const result_slice = ([]u8)((&result)[0...1]);
-    for (result_slice) |*b, i| {
-        *b = x_slice[@sizeOf(T) - i - 1];
-    }
-    return result;
-}
std/os.zig
@@ -4,7 +4,7 @@ const errno = @import("errno.zig");
 pub error SigInterrupt;
 pub error Unexpected;
 
-pub fn get_random_bytes(buf: []u8) -> %void {
+pub fn getRandomBytes(buf: []u8) -> %void {
     switch (@compileVar("os")) {
         linux => {
             const ret = linux.getrandom(buf.ptr, buf.len, 0);
@@ -18,14 +18,18 @@ pub fn get_random_bytes(buf: []u8) -> %void {
                 }
             }
         },
-        else => @compile_err("unsupported os"),
+        else => @compileErr("unsupported os"),
     }
 }
 
 #attribute("cold")
 pub fn abort() -> unreachable {
-    linux.raise(linux.SIGABRT);
-    linux.raise(linux.SIGKILL);
-    while (true) {}
+    switch (@compileVar("os")) {
+        linux => {
+            linux.raise(linux.SIGABRT);
+            linux.raise(linux.SIGKILL);
+            while (true) {}
+        },
+        else => @compileErr("unsupported os"),
+    }
 }
-
std/rand.zig
@@ -87,7 +87,7 @@ pub struct Rand {
         } else if (T == f64) {
             9007199254740992
         } else {
-            @compile_err("unknown floating point type" ++ @typeName(T))
+            @compileErr("unknown floating point type" ++ @typeName(T))
         };
         return T(r.rangeUnsigned(int_type, 0, precision)) / T(precision);
     }
CMakeLists.txt
@@ -200,27 +200,29 @@ install(FILES ${C_HEADERS} DESTINATION ${C_HEADERS_DEST})
 install(FILES "${CMAKE_SOURCE_DIR}/std/bootstrap.zig" DESTINATION "${ZIG_STD_DEST}")
 install(FILES "${CMAKE_SOURCE_DIR}/std/builtin.zig" DESTINATION "${ZIG_STD_DEST}")
 install(FILES "${CMAKE_SOURCE_DIR}/std/compiler_rt.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/test_runner.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/test_runner_libc.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/test_runner_nolibc.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/io.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/net.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/os.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/str.zig" DESTINATION "${ZIG_STD_DEST}")
 install(FILES "${CMAKE_SOURCE_DIR}/std/cstr.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/linux.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/debug.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/elf.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/empty.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/endian.zig" DESTINATION "${ZIG_STD_DEST}")
 install(FILES "${CMAKE_SOURCE_DIR}/std/errno.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/rand.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/rand_test.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/math.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/hash_map.zig" DESTINATION "${ZIG_STD_DEST}")
 install(FILES "${CMAKE_SOURCE_DIR}/std/index.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/linux_x86_64.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/io.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/linux.zig" DESTINATION "${ZIG_STD_DEST}")
 install(FILES "${CMAKE_SOURCE_DIR}/std/linux_i386.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/mem.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/linux_x86_64.zig" DESTINATION "${ZIG_STD_DEST}")
 install(FILES "${CMAKE_SOURCE_DIR}/std/list.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/hash_map.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/empty.zig" DESTINATION "${ZIG_STD_DEST}")
-install(FILES "${CMAKE_SOURCE_DIR}/std/debug.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/math.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/mem.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/net.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/os.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/rand.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/rand_test.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/str.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/test_runner.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/test_runner_libc.zig" DESTINATION "${ZIG_STD_DEST}")
+install(FILES "${CMAKE_SOURCE_DIR}/std/test_runner_nolibc.zig" DESTINATION "${ZIG_STD_DEST}")
 
 add_executable(run_tests ${TEST_SOURCES})
 target_link_libraries(run_tests)