tiny.profiling.substitute

1pub const substitute = @import("substitute.zig");

1const std = @import("std");23pub const Replacement = struct {4    token: []const u8,5    value: []const u8,6};78pub fn resolve(9    allocator: std.mem.Allocator,10    template: []const u8,11    replacements: []const Replacement,12    maximum_bytes: usize,13) ![]const u8 {14    if (maximum_bytes == 0 or std.mem.indexOfScalar(u8, template, 0) != null) {15        return error.InvalidResolvedString;16    }17    for (replacements) |replacement| {18        if (replacement.token.len == 0 or19            std.mem.indexOfScalar(u8, replacement.token, 0) != null or20            std.mem.indexOfScalar(u8, replacement.value, 0) != null)21        {22            return error.InvalidResolvedString;23        }24    }25    if (template.len > maximum_bytes) return error.InvalidResolvedString;26    var result = template;27    var owned: ?[]u8 = null;28    errdefer if (owned) |bytes| allocator.free(bytes);29    for (replacements) |replacement| {30        const next = try replace(31            allocator,32            result,33            replacement,34            maximum_bytes,35        ) orelse continue;36        if (owned) |bytes| allocator.free(bytes);37        result = next;38        owned = next;39    }40    return result;41}4243fn replace(44    allocator: std.mem.Allocator,45    input: []const u8,46    replacement: Replacement,47    maximum_bytes: usize,48) !?[]u8 {49    const count = std.mem.count(u8, input, replacement.token);50    if (count == 0) return null;51    const removed = std.math.mul(usize, count, replacement.token.len) catch52        return error.InvalidResolvedString;53    const added = std.math.mul(usize, count, replacement.value.len) catch54        return error.InvalidResolvedString;55    const base = input.len - removed;56    const resolved_bytes = std.math.add(usize, base, added) catch57        return error.InvalidResolvedString;58    if (resolved_bytes > maximum_bytes) return error.InvalidResolvedString;59    const result = try allocator.alloc(u8, resolved_bytes);60    _ = std.mem.replace(61        u8,62        input,63        replacement.token,64        replacement.value,65        result,66    );67    return result;68}6970test "profiling substitutions resolve bounded repeated tokens once" {71    var arena_state = std.heap.ArenaAllocator.init(std.testing.allocator);72    defer arena_state.deinit();73    const allocator = arena_state.allocator();74    const result = try resolve(allocator, "{root}/{side}/{root}", &.{75        .{ .token = "{root}", .value = "/tmp/{side}" },76        .{ .token = "{side}", .value = "candidate" },77    }, 128);78    try std.testing.expectEqualStrings(79        "/tmp/candidate/candidate//tmp/candidate",80        result,81    );82    try std.testing.expectEqualStrings(83        "literal",84        try resolve(allocator, "literal", &.{}, 7),85    );86    try std.testing.expectEqualStrings(87        "",88        try resolve(allocator, "", &.{}, 1),89    );90    try std.testing.expectEqualStrings(91        "12345678",92        try resolve(allocator, "{value}", &.{.{93            .token = "{value}",94            .value = "12345678",95        }}, 8),96    );97    try std.testing.expectError(98        error.InvalidResolvedString,99        resolve(allocator, "{value}", &.{.{100            .token = "{value}",101            .value = "123456789",102        }}, 8),103    );104}