Function ftruncate [src]

Length must be positive when treated as an i64.

Prototype

pub fn ftruncate(fd: fd_t, length: u64) TruncateError!void

Parameters

fd: fd_tlength: u64

Possible Errors

AccessDenied

FileBusy

FileTooBig

InputOutput

PermissionDenied

Unexpected UnexpectedError

The Operating System returned an undocumented error code.

This error is in theory not possible, but it would be better to handle this error than to invoke undefined behavior.

When this error code is observed, it usually means the Zig Standard Library needs a small patch to add the error code to the error set for the respective function.

Source

  pub fn ftruncate(fd: fd_t, length: u64) TruncateError!void {
    const signed_len: i64 = @bitCast(length);
    if (signed_len < 0) return error.FileTooBig; // avoid ambiguous EINVAL errors

    if (native_os == .windows) {
        var io_status_block: windows.IO_STATUS_BLOCK = undefined;
        var eof_info = windows.FILE_END_OF_FILE_INFORMATION{
            .EndOfFile = signed_len,
        };

        const rc = windows.ntdll.NtSetInformationFile(
            fd,
            &io_status_block,
            &eof_info,
            @sizeOf(windows.FILE_END_OF_FILE_INFORMATION),
            .FileEndOfFileInformation,
        );

        switch (rc) {
            .SUCCESS => return,
            .INVALID_HANDLE => unreachable, // Handle not open for writing
            .ACCESS_DENIED => return error.AccessDenied,
            .USER_MAPPED_FILE => return error.AccessDenied,
            .INVALID_PARAMETER => return error.FileTooBig,
            else => return windows.unexpectedStatus(rc),
        }
    }
    if (native_os == .wasi and !builtin.link_libc) {
        switch (wasi.fd_filestat_set_size(fd, length)) {
            .SUCCESS => return,
            .INTR => unreachable,
            .FBIG => return error.FileTooBig,
            .IO => return error.InputOutput,
            .PERM => return error.PermissionDenied,
            .TXTBSY => return error.FileBusy,
            .BADF => unreachable, // Handle not open for writing
            .INVAL => unreachable, // Handle not open for writing, negative length, or non-resizable handle
            .NOTCAPABLE => return error.AccessDenied,
            else => |err| return unexpectedErrno(err),
        }
    }

    const ftruncate_sym = if (lfs64_abi) system.ftruncate64 else system.ftruncate;
    while (true) {
        switch (errno(ftruncate_sym(fd, signed_len))) {
            .SUCCESS => return,
            .INTR => continue,
            .FBIG => return error.FileTooBig,
            .IO => return error.InputOutput,
            .PERM => return error.PermissionDenied,
            .TXTBSY => return error.FileBusy,
            .BADF => unreachable, // Handle not open for writing
            .INVAL => unreachable, // Handle not open for writing, negative length, or non-resizable handle
            else => |err| return unexpectedErrno(err),
        }
    }
}  