path: root/src/os.cpp

/*
 * Copyright (c) 2015 Andrew Kelley
 *
 * This file is part of zig, which is MIT licensed.
 * See http://opensource.org/licenses/MIT
 */

#include "os.hpp"
#include "util.hpp"
#include "error.hpp"

#if defined(_WIN32)

#if !defined(NOMINMAX)
#define NOMINMAX
#endif

#if !defined(VC_EXTRALEAN)
#define VC_EXTRALEAN
#endif

#if !defined(WIN32_LEAN_AND_MEAN)
#define WIN32_LEAN_AND_MEAN
#endif

#include <windows.h>
#include <io.h>

typedef SSIZE_T ssize_t;
#else
#define ZIG_OS_POSIX

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <limits.h>

#endif


#if defined(__MACH__)
#include <mach/clock.h>
#include <mach/mach.h>
#endif

#if defined(ZIG_OS_WINDOWS)
static double win32_time_resolution;
#elif defined(__MACH__)
static clock_serv_t cclock;
#endif

#include <stdlib.h>
#include <errno.h>
#include <time.h>

// these implementations are lazy. But who cares, we'll make a robust
// implementation in the zig standard library and then this code all gets
// deleted when we self-host. it works for now.


#if defined(ZIG_OS_POSIX)
static void populate_termination(Termination *term, int status) {
    if (WIFEXITED(status)) {
        term->how = TerminationIdClean;
        term->code = WEXITSTATUS(status);
    } else if (WIFSIGNALED(status)) {
        term->how = TerminationIdSignaled;
        term->code = WTERMSIG(status);
    } else if (WIFSTOPPED(status)) {
        term->how = TerminationIdStopped;
        term->code = WSTOPSIG(status);
    } else {
        term->how = TerminationIdUnknown;
        term->code = status;
    }
}

static void os_spawn_process_posix(const char *exe, ZigList<const char *> &args, Termination *term) {
    pid_t pid = fork();
    if (pid == -1)
        zig_panic("fork failed");
    if (pid == 0) {
        // child
        const char **argv = allocate<const char *>(args.length + 2);
        argv[0] = exe;
        argv[args.length + 1] = nullptr;
        for (size_t i = 0; i < args.length; i += 1) {
            argv[i + 1] = args.at(i);
        }
        execvp(exe, const_cast<char * const *>(argv));
        zig_panic("execvp failed: %s", strerror(errno));
    } else {
        // parent
        int status;
        waitpid(pid, &status, 0);
        populate_termination(term, status);
    }
}
#endif

#if defined(ZIG_OS_WINDOWS)
static void os_spawn_process_windows(const char *exe, ZigList<const char *> &args, Termination *term) {
    Buf stderr_buf = BUF_INIT;
    Buf stdout_buf = BUF_INIT;

    // TODO this is supposed to inherit stdout/stderr instead of capturing it
    os_exec_process(exe, args, term, &stderr_buf, &stdout_buf);
    fwrite(buf_ptr(&stderr_buf), 1, buf_len(&stderr_buf), stderr);
    fwrite(buf_ptr(&stdout_buf), 1, buf_len(&stdout_buf), stdout);
}
#endif

void os_spawn_process(const char *exe, ZigList<const char *> &args, Termination *term) {
#if defined(ZIG_OS_WINDOWS)
    os_spawn_process_windows(exe, args, term);
#elif defined(ZIG_OS_POSIX)
    os_spawn_process_posix(exe, args, term);
#else
#error "missing os_spawn_process implementation"
#endif
}

void os_path_dirname(Buf *full_path, Buf *out_dirname) {
    return os_path_split(full_path, out_dirname, nullptr);
}

bool os_is_sep(uint8_t c) {
#if defined(ZIG_OS_WINDOWS)
    return c == '\\' || c == '/';
#else
    return c == '/';
#endif
}

void os_path_split(Buf *full_path, Buf *out_dirname, Buf *out_basename) {
    size_t len = buf_len(full_path);
    if (len != 0) {
        size_t last_index = len - 1;
        if (os_is_sep(buf_ptr(full_path)[last_index])) {
            last_index -= 1;
        }
        for (size_t i = last_index;;) {
            uint8_t c = buf_ptr(full_path)[i];
            if (os_is_sep(c)) {
                if (out_dirname) {
                    buf_init_from_mem(out_dirname, buf_ptr(full_path), i);
                }
                if (out_basename) {
                    buf_init_from_mem(out_basename, buf_ptr(full_path) + i + 1, buf_len(full_path) - (i + 1));
                }
                return;
            }
            if (i == 0) break;
            i -= 1;
        }
    }
    if (out_dirname) buf_init_from_mem(out_dirname, ".", 1);
    if (out_basename) buf_init_from_buf(out_basename, full_path);
}

void os_path_extname(Buf *full_path, Buf *out_basename, Buf *out_extname) {
    if (buf_len(full_path) == 0) {
        if (out_basename) buf_init_from_str(out_basename, "");
        if (out_extname) buf_init_from_str(out_extname, "");
        return;
    }
    size_t i = buf_len(full_path) - 1;
    while (true) {
        if (buf_ptr(full_path)[i] == '.') {
            if (out_basename) {
                buf_resize(out_basename, 0);
                buf_append_mem(out_basename, buf_ptr(full_path), i);
            }

            if (out_extname) {
                buf_resize(out_extname, 0);
                buf_append_mem(out_extname, buf_ptr(full_path) + i, buf_len(full_path) - i);
            }
            return;
        }

        if (i == 0) {
            if (out_basename) buf_init_from_buf(out_basename, full_path);
            if (out_extname) buf_init_from_str(out_extname, "");
            return;
        }
        i -= 1;
    }
}

void os_path_join(Buf *dirname, Buf *basename, Buf *out_full_path) {
    buf_init_from_buf(out_full_path, dirname);
    uint8_t c = *(buf_ptr(out_full_path) + buf_len(out_full_path) - 1);
    if (!os_is_sep(c))
        buf_append_char(out_full_path, '/');
    buf_append_buf(out_full_path, basename);
}

int os_path_real(Buf *rel_path, Buf *out_abs_path) {
#if defined(ZIG_OS_WINDOWS)
    buf_resize(out_abs_path, 4096);
    if (_fullpath(buf_ptr(out_abs_path), buf_ptr(rel_path), buf_len(out_abs_path)) == nullptr) {
        zig_panic("_fullpath failed");
    }
    buf_resize(out_abs_path, strlen(buf_ptr(out_abs_path)));
    return ErrorNone;
#elif defined(ZIG_OS_POSIX)
    buf_resize(out_abs_path, PATH_MAX + 1);
    char *result = realpath(buf_ptr(rel_path), buf_ptr(out_abs_path));
    if (!result) {
        int err = errno;
        if (err == EACCES) {
            return ErrorAccess;
        } else if (err == ENOENT) {
            return ErrorFileNotFound;
        } else if (err == ENOMEM) {
            return ErrorNoMem;
        } else {
            return ErrorFileSystem;
        }
    }
    buf_resize(out_abs_path, strlen(buf_ptr(out_abs_path)));
    return ErrorNone;
#else
#error "missing os_path_real implementation"
#endif
}

bool os_path_is_absolute(Buf *path) {
#if defined(ZIG_OS_WINDOWS)
    if (buf_starts_with_str(path, "/") || buf_starts_with_str(path, "\\"))
        return true;

    if (buf_len(path) >= 3 && buf_ptr(path)[1] == ':')
        return true;

    return false;
#elif defined(ZIG_OS_POSIX)
    return buf_ptr(path)[0] == '/';
#else
#error "missing os_path_is_absolute implementation"
#endif
}

void os_path_resolve(Buf *ref_path, Buf *target_path, Buf *out_abs_path) {
    if (os_path_is_absolute(target_path)) {
        buf_init_from_buf(out_abs_path, target_path);
        return;
    }

    os_path_join(ref_path, target_path, out_abs_path);
    return;
}

int os_fetch_file(FILE *f, Buf *out_buf) {
    static const ssize_t buf_size = 0x2000;
    buf_resize(out_buf, buf_size);
    ssize_t actual_buf_len = 0;
    for (;;) {
        size_t amt_read = fread(buf_ptr(out_buf) + actual_buf_len, 1, buf_size, f);
        actual_buf_len += amt_read;
        if (amt_read != buf_size) {
            if (feof(f)) {
                buf_resize(out_buf, actual_buf_len);
                return 0;
            } else {
                return ErrorFileSystem;
            }
        }

        buf_resize(out_buf, actual_buf_len + buf_size);
    }
    zig_unreachable();
}

int os_file_exists(Buf *full_path, bool *result) {
#if defined(ZIG_OS_POSIX)
    *result = access(buf_ptr(full_path), F_OK) != -1;
    return 0;
#else
    return GetFileAttributes(buf_ptr(full_path)) != INVALID_FILE_ATTRIBUTES;
#endif
}

#if defined(ZIG_OS_POSIX)
static int os_exec_process_posix(const char *exe, ZigList<const char *> &args,
        Termination *term, Buf *out_stderr, Buf *out_stdout)
{
    int stdin_pipe[2];
    int stdout_pipe[2];
    int stderr_pipe[2];

    int err;
    if ((err = pipe(stdin_pipe)))
        zig_panic("pipe failed");
    if ((err = pipe(stdout_pipe)))
        zig_panic("pipe failed");
    if ((err = pipe(stderr_pipe)))
        zig_panic("pipe failed");

    pid_t pid = fork();
    if (pid == -1)
        zig_panic("fork failed");
    if (pid == 0) {
        // child
        if (dup2(stdin_pipe[0], STDIN_FILENO) == -1)
            zig_panic("dup2 failed");

        if (dup2(stdout_pipe[1], STDOUT_FILENO) == -1)
            zig_panic("dup2 failed");

        if (dup2(stderr_pipe[1], STDERR_FILENO) == -1)
            zig_panic("dup2 failed");

        const char **argv = allocate<const char *>(args.length + 2);
        argv[0] = exe;
        argv[args.length + 1] = nullptr;
        for (size_t i = 0; i < args.length; i += 1) {
            argv[i + 1] = args.at(i);
        }
        execvp(exe, const_cast<char * const *>(argv));
        if (errno == ENOENT) {
            return ErrorFileNotFound;
        } else {
            zig_panic("execvp failed: %s", strerror(errno));
        }
    } else {
        // parent
        close(stdin_pipe[0]);
        close(stdin_pipe[1]);
        close(stdout_pipe[1]);
        close(stderr_pipe[1]);

        int status;
        waitpid(pid, &status, 0);
        populate_termination(term, status);

        FILE *stdout_f = fdopen(stdout_pipe[0], "rb");
        FILE *stderr_f = fdopen(stderr_pipe[0], "rb");
        os_fetch_file(stdout_f, out_stdout);
        os_fetch_file(stderr_f, out_stderr);

        fclose(stdout_f);
        fclose(stderr_f);

        return 0;
    }
}
#endif

#if defined(ZIG_OS_WINDOWS)

/*
static void win32_panic(const char *str) {
    DWORD err = GetLastError();
    LPSTR messageBuffer = nullptr;
    FormatMessageA(
        FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
        NULL, err, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), (LPSTR)&messageBuffer, 0, NULL);
    zig_panic(str, messageBuffer);
    LocalFree(messageBuffer);
}
*/

static int os_exec_process_windows(const char *exe, ZigList<const char *> &args,
        Termination *term, Buf *out_stderr, Buf *out_stdout)
{
    Buf command_line = BUF_INIT;
    buf_resize(&command_line, 0);

    buf_append_char(&command_line, '\"');
    buf_append_str(&command_line, exe);
    buf_append_char(&command_line, '\"');

    for (size_t arg_i = 0; arg_i < args.length; arg_i += 1) {
        buf_append_str(&command_line, " \"");
        const char *arg = args.at(arg_i);
        size_t arg_len = strlen(arg);
        for (size_t c_i = 0; c_i < arg_len; c_i += 1) {
            if (arg[c_i] == '\"') {
                zig_panic("TODO");
            }
            buf_append_char(&command_line, arg[c_i]);
        }
        buf_append_char(&command_line, '\"');
    }


    HANDLE g_hChildStd_IN_Rd = NULL;
    HANDLE g_hChildStd_IN_Wr = NULL;
    HANDLE g_hChildStd_OUT_Rd = NULL;
    HANDLE g_hChildStd_OUT_Wr = NULL;
    HANDLE g_hChildStd_ERR_Rd = NULL;
    HANDLE g_hChildStd_ERR_Wr = NULL;

    SECURITY_ATTRIBUTES saAttr;
    saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
    saAttr.bInheritHandle = TRUE;
    saAttr.lpSecurityDescriptor = NULL;

    if (!CreatePipe(&g_hChildStd_OUT_Rd, &g_hChildStd_OUT_Wr, &saAttr, 0)) {
        zig_panic("StdoutRd CreatePipe");
    }

    if (!SetHandleInformation(g_hChildStd_OUT_Rd, HANDLE_FLAG_INHERIT, 0)) {
        zig_panic("Stdout SetHandleInformation");
    }

    if (!CreatePipe(&g_hChildStd_ERR_Rd, &g_hChildStd_ERR_Wr, &saAttr, 0)) {
        zig_panic("stderr CreatePipe");
    }

    if (!SetHandleInformation(g_hChildStd_ERR_Rd, HANDLE_FLAG_INHERIT, 0)) {
        zig_panic("stderr SetHandleInformation");
    }

    if (!CreatePipe(&g_hChildStd_IN_Rd, &g_hChildStd_IN_Wr, &saAttr, 0)) {
        zig_panic("Stdin CreatePipe");
    }

    if (!SetHandleInformation(g_hChildStd_IN_Wr, HANDLE_FLAG_INHERIT, 0)) {
        zig_panic("Stdin SetHandleInformation");
    }


    PROCESS_INFORMATION piProcInfo = {0};
    STARTUPINFO siStartInfo = {0};
    siStartInfo.cb = sizeof(STARTUPINFO);
    siStartInfo.hStdError = g_hChildStd_ERR_Wr;
    siStartInfo.hStdOutput = g_hChildStd_OUT_Wr;
    siStartInfo.hStdInput = g_hChildStd_IN_Rd;
    siStartInfo.dwFlags |= STARTF_USESTDHANDLES;

    BOOL success = CreateProcess(exe, buf_ptr(&command_line), nullptr, nullptr, TRUE, 0, nullptr, nullptr,
            &siStartInfo, &piProcInfo);

    if (!success) {
        if (GetLastError() == ERROR_FILE_NOT_FOUND) {
            CloseHandle(piProcInfo.hProcess);
            CloseHandle(piProcInfo.hThread);
            return ErrorFileNotFound;
        }
        zig_panic("CreateProcess failed. exe: %s command_line: %s", exe, buf_ptr(&command_line));
    }

    if (!CloseHandle(g_hChildStd_IN_Wr)) {
        zig_panic("stdinwr closehandle");
    }

    CloseHandle(g_hChildStd_IN_Rd);
    CloseHandle(g_hChildStd_ERR_Wr);
    CloseHandle(g_hChildStd_OUT_Wr);

    static const size_t BUF_SIZE = 4 * 1024;
    {
        DWORD dwRead;
        char chBuf[BUF_SIZE];

        buf_resize(out_stdout, 0);
        for (;;) {
            success = ReadFile( g_hChildStd_OUT_Rd, chBuf, BUF_SIZE, &dwRead, NULL);
            if (!success || dwRead == 0) break;

            buf_append_mem(out_stdout, chBuf, dwRead);
        }
        CloseHandle(g_hChildStd_OUT_Rd);
    }
    {
        DWORD dwRead;
        char chBuf[BUF_SIZE];

        buf_resize(out_stderr, 0);
        for (;;) {
            success = ReadFile( g_hChildStd_ERR_Rd, chBuf, BUF_SIZE, &dwRead, NULL);
            if (!success || dwRead == 0) break;

            buf_append_mem(out_stderr, chBuf, dwRead);
        }
        CloseHandle(g_hChildStd_ERR_Rd);
    }

    WaitForSingleObject(piProcInfo.hProcess, INFINITE);

    DWORD exit_code;
    if (!GetExitCodeProcess(piProcInfo.hProcess, &exit_code)) {
        zig_panic("GetExitCodeProcess failed");
    }
    term->how = TerminationIdClean;
    term->code = exit_code;

    CloseHandle(piProcInfo.hProcess);
    CloseHandle(piProcInfo.hThread);

    return 0;
}
#endif

int os_exec_process(const char *exe, ZigList<const char *> &args,
        Termination *term, Buf *out_stderr, Buf *out_stdout)
{
#if defined(ZIG_OS_WINDOWS)
    return os_exec_process_windows(exe, args, term, out_stderr, out_stdout);
#elif defined(ZIG_OS_POSIX)
    return os_exec_process_posix(exe, args, term, out_stderr, out_stdout);
#else
#error "missing os_exec_process implementation"
#endif
}

void os_write_file(Buf *full_path, Buf *contents) {
    FILE *f = fopen(buf_ptr(full_path), "wb");
    if (!f) {
        zig_panic("open failed");
    }
    size_t amt_written = fwrite(buf_ptr(contents), 1, buf_len(contents), f);
    if (amt_written != (size_t)buf_len(contents))
        zig_panic("write failed: %s", strerror(errno));
    if (fclose(f))
        zig_panic("close failed");
}

int os_copy_file(Buf *src_path, Buf *dest_path) {
    FILE *src_f = fopen(buf_ptr(src_path), "rb");
    if (!src_f) {
        int err = errno;
        if (err == ENOENT) {
            return ErrorFileNotFound;
        } else if (err == EACCES || err == EPERM) {
            return ErrorAccess;
        } else {
            return ErrorFileSystem;
        }
    }
    FILE *dest_f = fopen(buf_ptr(dest_path), "wb");
    if (!dest_f) {
        int err = errno;
        if (err == ENOENT) {
            fclose(src_f);
            return ErrorFileNotFound;
        } else if (err == EACCES || err == EPERM) {
            fclose(src_f);
            return ErrorAccess;
        } else {
            fclose(src_f);
            return ErrorFileSystem;
        }
    }

    static const size_t buf_size = 2048;
    char buf[buf_size];
    for (;;) {
        size_t amt_read = fread(buf, 1, buf_size, src_f);
        if (amt_read != buf_size) {
            if (ferror(src_f)) {
                fclose(src_f);
                fclose(dest_f);
                return ErrorFileSystem;
            }
        }
        size_t amt_written = fwrite(buf, 1, amt_read, dest_f);
        if (amt_written != amt_read) {
            fclose(src_f);
            fclose(dest_f);
            return ErrorFileSystem;
        }
        if (feof(src_f)) {
            fclose(src_f);
            fclose(dest_f);
            return 0;
        }
    }
}

int os_fetch_file_path(Buf *full_path, Buf *out_contents) {
    FILE *f = fopen(buf_ptr(full_path), "rb");
    if (!f) {
        switch (errno) {
            case EACCES:
                return ErrorAccess;
            case EINTR:
                return ErrorInterrupted;
            case EINVAL:
                zig_unreachable();
            case ENFILE:
            case ENOMEM:
                return ErrorSystemResources;
            case ENOENT:
                return ErrorFileNotFound;
            default:
                return ErrorFileSystem;
        }
    }
    int result = os_fetch_file(f, out_contents);
    fclose(f);
    return result;
}

int os_get_cwd(Buf *out_cwd) {
#if defined(ZIG_OS_WINDOWS)
    buf_resize(out_cwd, 4096);
    if (GetCurrentDirectory(buf_len(out_cwd), buf_ptr(out_cwd)) == 0) {
        zig_panic("GetCurrentDirectory failed");
    }
    return 0;
#elif defined(ZIG_OS_POSIX)
    int err = ERANGE;
    buf_resize(out_cwd, 512);
    while (err == ERANGE) {
        buf_resize(out_cwd, buf_len(out_cwd) * 2);
        err = getcwd(buf_ptr(out_cwd), buf_len(out_cwd)) ? 0 : errno;
    }
    if (err)
        zig_panic("unable to get cwd: %s", strerror(err));

    return 0;
#else
#error "missing os_get_cwd implementation"
#endif
}

bool os_stderr_tty(void) {
#if defined(ZIG_OS_WINDOWS)
    return _isatty(_fileno(stderr)) != 0;
#elif defined(ZIG_OS_POSIX)
    return isatty(STDERR_FILENO) != 0;
#else
#error "missing os_stderr_tty implementation"
#endif
}

#if defined(ZIG_OS_POSIX)
static int os_buf_to_tmp_file_posix(Buf *contents, Buf *suffix, Buf *out_tmp_path) {
    const char *tmp_dir = getenv("TMPDIR");
    if (!tmp_dir) {
        tmp_dir = P_tmpdir;
    }
    buf_resize(out_tmp_path, 0);
    buf_appendf(out_tmp_path, "%s/XXXXXX%s", tmp_dir, buf_ptr(suffix));

    int fd = mkstemps(buf_ptr(out_tmp_path), (int)buf_len(suffix));
    if (fd < 0) {
        return ErrorFileSystem;
    }

    FILE *f = fdopen(fd, "wb");
    if (!f) {
        zig_panic("fdopen failed");
    }

    size_t amt_written = fwrite(buf_ptr(contents), 1, buf_len(contents), f);
    if (amt_written != (size_t)buf_len(contents))
        zig_panic("write failed: %s", strerror(errno));
    if (fclose(f))
        zig_panic("close failed");

    return 0;
}
#endif

#if defined(ZIG_OS_WINDOWS)
static int os_buf_to_tmp_file_windows(Buf *contents, Buf *suffix, Buf *out_tmp_path) {
    char tmp_dir[MAX_PATH + 1];
    if (GetTempPath(MAX_PATH, tmp_dir) == 0) {
        zig_panic("GetTempPath failed");
    }
    buf_init_from_str(out_tmp_path, tmp_dir);

    const char base64[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_";
    assert(array_length(base64) == 64 + 1);
    for (size_t i = 0; i < 8; i += 1) {
        buf_append_char(out_tmp_path, base64[rand() % 64]);
    }

    buf_append_buf(out_tmp_path, suffix);

    FILE *f = fopen(buf_ptr(out_tmp_path), "wb");

    if (!f) {
        zig_panic("unable to open %s: %s", buf_ptr(out_tmp_path), strerror(errno));
    }

    size_t amt_written = fwrite(buf_ptr(contents), 1, buf_len(contents), f);
    if (amt_written != (size_t)buf_len(contents)) {
        zig_panic("write failed: %s", strerror(errno));
    }

    if (fclose(f)) {
        zig_panic("fclose failed");
    }
    return 0;
}
#endif

int os_buf_to_tmp_file(Buf *contents, Buf *suffix, Buf *out_tmp_path) {
#if defined(ZIG_OS_WINDOWS)
    return os_buf_to_tmp_file_windows(contents, suffix, out_tmp_path);
#elif defined(ZIG_OS_POSIX)
    return os_buf_to_tmp_file_posix(contents, suffix, out_tmp_path);
#else
#error "missing os_buf_to_tmp_file implementation"
#endif
}

int os_delete_file(Buf *path) {
    if (remove(buf_ptr(path))) {
        return ErrorFileSystem;
    } else {
        return 0;
    }
}

int os_rename(Buf *src_path, Buf *dest_path) {
    if (rename(buf_ptr(src_path), buf_ptr(dest_path)) == -1) {
        return ErrorFileSystem;
    }
    return 0;
}

double os_get_time(void) {
#if defined(ZIG_OS_WINDOWS)
    unsigned __int64 time;
    QueryPerformanceCounter((LARGE_INTEGER*) &time);
    return time * win32_time_resolution;
#elif defined(__MACH__)
    mach_timespec_t mts;

    kern_return_t err = clock_get_time(cclock, &mts);
    assert(!err);

    double seconds = (double)mts.tv_sec;
    seconds += ((double)mts.tv_nsec) / 1000000000.0;

    return seconds;
#else
    struct timespec tms;
    clock_gettime(CLOCK_MONOTONIC, &tms);
    double seconds = (double)tms.tv_sec;
    seconds += ((double)tms.tv_nsec) / 1000000000.0;
    return seconds;
#endif
}

int os_make_path(Buf *path) {
    Buf *resolved_path = buf_alloc();
    os_path_resolve(buf_create_from_str("."), path, resolved_path);

    size_t end_index = buf_len(resolved_path);
    int err;
    while (true) {
        if ((err = os_make_dir(buf_slice(resolved_path, 0, end_index)))) {
            if (err == ErrorPathAlreadyExists) {
                if (end_index == buf_len(resolved_path))
                    return 0;
            } else if (err == ErrorFileNotFound) {
                // march end_index backward until next path component
                while (true) {
                    end_index -= 1;
                    if (buf_ptr(resolved_path)[end_index] == '/')
                        break;
                }
                continue;
            } else {
                return err;
            }
        }
        if (end_index == buf_len(resolved_path))
            return 0;
        // march end_index forward until next path component
        while (true) {
            end_index += 1;
            if (end_index == buf_len(resolved_path) || buf_ptr(resolved_path)[end_index] == '/')
                break;
        }
    }
    return 0;
}

int os_make_dir(Buf *path) {
#if defined(ZIG_OS_WINDOWS)
    if (!CreateDirectory(buf_ptr(path), NULL)) {
        if (GetLastError() == ERROR_ALREADY_EXISTS)
            return ErrorPathAlreadyExists;
        if (GetLastError() == ERROR_PATH_NOT_FOUND)
            return ErrorFileNotFound;
        if (GetLastError() == ERROR_ACCESS_DENIED)
            return ErrorAccess;
        return ErrorUnexpected;
    }
    return 0;
#else
    if (mkdir(buf_ptr(path), 0755) == -1) {
        if (errno == EEXIST)
            return ErrorPathAlreadyExists;
        if (errno == ENOENT)
            return ErrorFileNotFound;
        if (errno == EACCES)
            return ErrorAccess;
        return ErrorUnexpected;
    }
    return 0;
#endif
}

int os_init(void) {
    srand((unsigned)time(NULL));
#if defined(ZIG_OS_WINDOWS)
    unsigned __int64 frequency;
    if (QueryPerformanceFrequency((LARGE_INTEGER*) &frequency)) {
        win32_time_resolution = 1.0 / (double) frequency;
    } else {
        return ErrorSystemResources;
    }
#elif defined(__MACH__)
    host_get_clock_service(mach_host_self(), SYSTEM_CLOCK, &cclock);
#endif
    return 0;
}