decamelize

Convert camelCase to a separated form: unicornRainbow → unicorn_rainbow.

const decamelize = @import("decamelize");

const a = try decamelize.decamelize(allocator, "unicornRainbow", .{}); // "unicorn_rainbow"
const b = try decamelize.decamelize(allocator, "myURLString", .{
    .preserve_consecutive_uppercase = true,
}); // "my_URL_string"
const c = try decamelize.decamelize(allocator, "unicornRainbow", .{ .separator = "-" }); // "unicorn-rainbow"
// Caller owns the returned memory.

Installation

Requires Zig 0.16.0.

zig fetch --save git+https://github.com/thelastbackspace/zig-decamelize#v1.0.0

Then in build.zig:

const decamelize = b.dependency("decamelize", .{ .target = target, .optimize = optimize });
exe.root_module.addImport("decamelize", decamelize.module("decamelize"));

API

decamelize(allocator, text: []const u8, options: Options) ![]u8

Convert one string. A separator is inserted at each lowercase-or-digit → uppercase transition, and before the last uppercase letter of an acronym followed by lowercase text (URLString → url_string). The result is lowercased. Caller owns the returned memory.

Options

• separator: []const u8 = "_" — inserted between words; may be any string, including empty.
• preserve_consecutive_uppercase: bool = false — keep acronym runs intact and lowercase only one-letter words: myURLString → my_URL_string, data_For_USACounties → data_for_USA_counties.

Notes

• Case mapping and letter classification use simple Unicode mappings (Unicode 16.0.0) generated into src/unicode_data.zig.
• Text is processed by Unicode code point.
• Input is expected to be valid UTF-8.

Testing

zig build test

The suite ports the upstream project's test file, including the long mixed-case strings and the pathological-input cases (those assert correctness here; the wall-clock bounds exist upstream to guard against regex backtracking, which a linear scan does not have).

Contributing

PRs welcome — see CONTRIBUTING.md. The CI gate (zig fmt --check, tests, build) must pass.

Credits

Behavior and the test suite follow the npm package decamelize v6.0.1 (MIT, © Sindre Sorhus); the implementation is original, and the Unicode tables are generated from the Unicode Character Database 16.0.0. Zig implementation © 2026 thelastbackspace, MIT — see LICENSE.