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const std = @import("std");
const testing = std.testing;
const Allocator = std.mem.Allocator;
const Writer = std.Io.Writer;
/// Builder for constructing space-separated shell command strings.
/// Uses a caller-provided allocator (typically with stackFallback).
pub const ShellCommandBuilder = struct {
buffer: std.Io.Writer.Allocating,
pub fn init(allocator: Allocator) ShellCommandBuilder {
return .{ .buffer = .init(allocator) };
}
pub fn deinit(self: *ShellCommandBuilder) void {
self.buffer.deinit();
}
/// Append an argument to the command with automatic space separation.
pub fn appendArg(self: *ShellCommandBuilder, arg: []const u8) (Allocator.Error || Writer.Error)!void {
if (arg.len == 0) return;
if (self.buffer.written().len > 0) {
try self.buffer.writer.writeByte(' ');
}
try self.buffer.writer.writeAll(arg);
}
/// Get the final null-terminated command string, transferring ownership to caller.
/// Calling deinit() after this is safe but unnecessary.
pub fn toOwnedSlice(self: *ShellCommandBuilder) Allocator.Error![:0]const u8 {
return try self.buffer.toOwnedSliceSentinel(0);
}
};
test ShellCommandBuilder {
// Empty command
{
var cmd = ShellCommandBuilder.init(testing.allocator);
defer cmd.deinit();
try testing.expectEqualStrings("", cmd.buffer.written());
}
// Single arg
{
var cmd = ShellCommandBuilder.init(testing.allocator);
defer cmd.deinit();
try cmd.appendArg("bash");
try testing.expectEqualStrings("bash", cmd.buffer.written());
}
// Multiple args
{
var cmd = ShellCommandBuilder.init(testing.allocator);
defer cmd.deinit();
try cmd.appendArg("bash");
try cmd.appendArg("--posix");
try cmd.appendArg("-l");
try testing.expectEqualStrings("bash --posix -l", cmd.buffer.written());
}
// Empty arg
{
var cmd = ShellCommandBuilder.init(testing.allocator);
defer cmd.deinit();
try cmd.appendArg("bash");
try cmd.appendArg("");
try testing.expectEqualStrings("bash", cmd.buffer.written());
}
// toOwnedSlice
{
var cmd = ShellCommandBuilder.init(testing.allocator);
try cmd.appendArg("bash");
try cmd.appendArg("--posix");
const result = try cmd.toOwnedSlice();
defer testing.allocator.free(result);
try testing.expectEqualStrings("bash --posix", result);
try testing.expectEqual(@as(u8, 0), result[result.len]);
}
}
/// Writer that escapes characters that shells treat specially to reduce the
/// risk of injection attacks or other such weirdness. Specifically excludes
/// linefeeds so that they can be used to delineate lists of file paths.
pub const ShellEscapeWriter = struct {
writer: Writer,
child: *Writer,
pub fn init(child: *Writer) ShellEscapeWriter {
return .{
.writer = .{
// TODO: Actually use a buffer here
.buffer = &.{},
.vtable = &.{ .drain = ShellEscapeWriter.drain },
},
.child = child,
};
}
fn drain(w: *Writer, data: []const []const u8, splat: usize) Writer.Error!usize {
const self: *ShellEscapeWriter = @fieldParentPtr("writer", w);
// TODO: This is a very naive implementation and does not really make
// full use of the post-Writergate API. However, since we know that
// this is going into an Allocating writer anyways, we can be a bit
// less strict here.
var count: usize = 0;
for (data[0 .. data.len - 1]) |chunk| try self.writeEscaped(chunk, &count);
for (0..splat) |_| try self.writeEscaped(data[data.len - 1], &count);
return count;
}
fn writeEscaped(
self: *ShellEscapeWriter,
s: []const u8,
count: *usize,
) Writer.Error!void {
for (s) |byte| {
const buf = switch (byte) {
'\\',
'"',
'\'',
'$',
'`',
'*',
'?',
' ',
'|',
'(',
')',
=> &[_]u8{ '\\', byte },
else => &[_]u8{byte},
};
try self.child.writeAll(buf);
count.* += 1;
}
}
};
test "shell escape 1" {
var buf: [128]u8 = undefined;
var writer: std.Io.Writer = .fixed(&buf);
var shell: ShellEscapeWriter = .init(&writer);
try shell.writer.writeAll("abc");
try testing.expectEqualStrings("abc", writer.buffered());
}
test "shell escape 2" {
var buf: [128]u8 = undefined;
var writer: std.Io.Writer = .fixed(&buf);
var shell: ShellEscapeWriter = .init(&writer);
try shell.writer.writeAll("a c");
try testing.expectEqualStrings("a\\ c", writer.buffered());
}
test "shell escape 3" {
var buf: [128]u8 = undefined;
var writer: std.Io.Writer = .fixed(&buf);
var shell: ShellEscapeWriter = .init(&writer);
try shell.writer.writeAll("a?c");
try testing.expectEqualStrings("a\\?c", writer.buffered());
}
test "shell escape 4" {
var buf: [128]u8 = undefined;
var writer: std.Io.Writer = .fixed(&buf);
var shell: ShellEscapeWriter = .init(&writer);
try shell.writer.writeAll("a\\c");
try testing.expectEqualStrings("a\\\\c", writer.buffered());
}
test "shell escape 5" {
var buf: [128]u8 = undefined;
var writer: std.Io.Writer = .fixed(&buf);
var shell: ShellEscapeWriter = .init(&writer);
try shell.writer.writeAll("a|c");
try testing.expectEqualStrings("a\\|c", writer.buffered());
}
test "shell escape 6" {
var buf: [128]u8 = undefined;
var writer: std.Io.Writer = .fixed(&buf);
var shell: ShellEscapeWriter = .init(&writer);
try shell.writer.writeAll("a\"c");
try testing.expectEqualStrings("a\\\"c", writer.buffered());
}
test "shell escape 7" {
var buf: [128]u8 = undefined;
var writer: std.Io.Writer = .fixed(&buf);
var shell: ShellEscapeWriter = .init(&writer);
try shell.writer.writeAll("a(1)");
try testing.expectEqualStrings("a\\(1\\)", writer.buffered());
}
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