parseEscapeSequence

Parse an escape sequence from slice[offset..]. If parsing is successful, offset is updated to reflect the characters consumed.

Function parameters

Parameters

slice:[]const u8
offset:*usize

Type definitions in this namespace

Types

ParsedCharLiteral
Result
Error

Asserts the slice starts and ends with single-quotes.

Functions

parseCharLiteral: Asserts the slice starts and ends with single-quotes.
parseEscapeSequence: Parse an escape sequence from `slice[offset..]`.
parseWrite: Parses `bytes` as a Zig string literal and writes the result to the `Writer` type.
parseAlloc: Higher level API.

Error sets in this namespace

Error Sets

ParseError

Source

Implementation

pub fn parseEscapeSequence(slice: []const u8, offset: *usize) ParsedCharLiteral {
    assert(slice.len > offset.*);
    assert(slice[offset.*] == '\\');

    if (slice.len == offset.* + 1)
        return .{ .failure = .{ .invalid_escape_character = offset.* + 1 } };

    offset.* += 2;
    switch (slice[offset.* - 1]) {
        'n' => return .{ .success = '\n' },
        'r' => return .{ .success = '\r' },
        '\\' => return .{ .success = '\\' },
        't' => return .{ .success = '\t' },
        '\'' => return .{ .success = '\'' },
        '"' => return .{ .success = '"' },
        'x' => {
            var value: u8 = 0;
            var i: usize = offset.*;
            while (i < offset.* + 2) : (i += 1) {
                if (i == slice.len) return .{ .failure = .{ .expected_hex_digit = i } };

                const c = slice[i];
                switch (c) {
                    '0'...'9' => {
                        value *= 16;
                        value += c - '0';
                    },
                    'a'...'f' => {
                        value *= 16;
                        value += c - 'a' + 10;
                    },
                    'A'...'F' => {
                        value *= 16;
                        value += c - 'A' + 10;
                    },
                    else => {
                        return .{ .failure = .{ .expected_hex_digit = i } };
                    },
                }
            }
            offset.* = i;
            return .{ .success = value };
        },
        'u' => {
            var i: usize = offset.*;
            if (i >= slice.len or slice[i] != '{') return .{ .failure = .{ .expected_lbrace = i } };
            i += 1;
            if (i >= slice.len) return .{ .failure = .{ .expected_hex_digit_or_rbrace = i } };
            if (slice[i] == '}') return .{ .failure = .{ .empty_unicode_escape_sequence = i } };

            var value: u32 = 0;
            while (i < slice.len) : (i += 1) {
                const c = slice[i];
                switch (c) {
                    '0'...'9' => {
                        value *= 16;
                        value += c - '0';
                    },
                    'a'...'f' => {
                        value *= 16;
                        value += c - 'a' + 10;
                    },
                    'A'...'F' => {
                        value *= 16;
                        value += c - 'A' + 10;
                    },
                    '}' => {
                        i += 1;
                        break;
                    },
                    else => return .{ .failure = .{ .expected_hex_digit_or_rbrace = i } },
                }
                if (value > 0x10ffff) {
                    return .{ .failure = .{ .invalid_unicode_codepoint = i } };
                }
            } else {
                return .{ .failure = .{ .expected_rbrace = i } };
            }
            offset.* = i;
            return .{ .success = @as(u21, @intCast(value)) };
        },
        else => return .{ .failure = .{ .invalid_escape_character = offset.* - 1 } },
    }
}