feat(php-src): add a BSD-licensed crate for php-src derived code

The audit in .ken/php-shim-copying.md judged 14 functions in
shirabe-php-shim (plus php_wordwrap in shirabe-external-packages) to be
line-by-line transcriptions or structural imitations of php-src. PHP's
relicensing to 3-clause BSD makes keeping them legal, but the boundary
between BSD-derived and MIT code was invisible in the source tree.

Moving them into their own crate puts the license into the build
metadata (so NOTICE generation follows the binary), makes a reverse
dependency a compile error, and encodes the origin in the module path,
which mirrors php-src's ext tree. Each function records its origin in a
fixed-format doc comment, and a new php_src_derivation_boundary linter
fails if `php-src` appears in any Rust source outside the crate.

Public paths under shirabe_php_shim:: are unchanged: functions that are
themselves derived are re-exported with `pub use`, and the wrappers that
only validate arguments stay on the MIT side.

This also resolves the duplicate wordwrap implementation.
shirabe_php_shim::wordwrap was todo!(), so SymfonyStyle::block panicked,
while shirabe-external-packages carried its own copy. Both now go
through the single port, verified against real PHP on 13 cases covering
multi-character breaks and cut.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

1 files changed, 146 insertions, 0 deletions

diff --git a/crates/shirabe-php-src/src/standard/strnatcmp.rs b/crates/shirabe-php-src/src/standard/strnatcmp.rs
new file mode 100644
index 00000000..30f4176a
--- /dev/null
+++ b/crates/shirabe-php-src/src/standard/strnatcmp.rs
@@ -0,0 +1,146 @@
+/// php-src: ext/standard/strnatcmp.c `strnatcmp_ex` (PHP 8.5.2)
+///
+/// Operating on byte slices, an out-of-range index reads as 0, reproducing the NUL terminator
+/// that the C implementation relies on.
+pub fn strnatcmp_ex(a: &[u8], b: &[u8], fold_case: bool) -> i64 {
+    let a_len = a.len();
+    let b_len = b.len();
+    if a_len == 0 || b_len == 0 {
+        return match a_len.cmp(&b_len) {
+            std::cmp::Ordering::Less => -1,
+            std::cmp::Ordering::Greater => 1,
+            std::cmp::Ordering::Equal => 0,
+        };
+    }
+
+    let mut ap = 0usize;
+    let mut bp = 0usize;
+    let mut leading = true;
+    loop {
+        let mut ca = natcmp_at(a, ap);
+        let mut cb = natcmp_at(b, bp);
+
+        // Skip over leading zeros.
+        while leading && ca == b'0' && natcmp_at(a, ap + 1).is_ascii_digit() {
+            ap += 1;
+            ca = natcmp_at(a, ap);
+        }
+        while leading && cb == b'0' && natcmp_at(b, bp + 1).is_ascii_digit() {
+            bp += 1;
+            cb = natcmp_at(b, bp);
+        }
+        leading = false;
+
+        // Skip consecutive whitespace.
+        while natcmp_is_space(ca) {
+            ap += 1;
+            ca = natcmp_at(a, ap);
+        }
+        while natcmp_is_space(cb) {
+            bp += 1;
+            cb = natcmp_at(b, bp);
+        }
+
+        // Process a run of digits.
+        if ca.is_ascii_digit() && cb.is_ascii_digit() {
+            let fractional = ca == b'0' || cb == b'0';
+            let result = if fractional {
+                natcmp_compare_left(a, &mut ap, b, &mut bp)
+            } else {
+                natcmp_compare_right(a, &mut ap, b, &mut bp)
+            };
+            if result != 0 {
+                return result;
+            }
+        }
+
+        if ap == a_len && bp == b_len {
+            return 0;
+        } else if ap == a_len {
+            return -1;
+        } else if bp == b_len {
+            return 1;
+        }
+
+        if fold_case {
+            ca = natcmp_at(a, ap).to_ascii_uppercase();
+            cb = natcmp_at(b, bp).to_ascii_uppercase();
+        } else {
+            ca = natcmp_at(a, ap);
+            cb = natcmp_at(b, bp);
+        }
+
+        if ca < cb {
+            return -1;
+        } else if ca > cb {
+            return 1;
+        }
+
+        ap += 1;
+        bp += 1;
+    }
+}
+
+/// php-src: ext/standard/strnatcmp.c (no direct counterpart) (PHP 8.5.2)
+fn natcmp_at(s: &[u8], i: usize) -> u8 {
+    if i < s.len() { s[i] } else { 0 }
+}
+
+/// php-src: ext/standard/strnatcmp.c `isspace(3)` usage (PHP 8.5.2)
+fn natcmp_is_space(c: u8) -> bool {
+    matches!(c, b' ' | b'\t' | b'\n' | 0x0b | 0x0c | b'\r')
+}
+
+/// php-src: ext/standard/strnatcmp.c `compare_right` (PHP 8.5.2)
+///
+/// Compare two right-aligned numbers: the longest run of digits wins; failing that, the first
+/// differing digit decides, but only once magnitudes are known equal (tracked in `bias`).
+fn natcmp_compare_right(a: &[u8], ap: &mut usize, b: &[u8], bp: &mut usize) -> i64 {
+    let mut bias = 0i64;
+    loop {
+        let ca = natcmp_at(a, *ap);
+        let cb = natcmp_at(b, *bp);
+        let a_digit = ca.is_ascii_digit();
+        let b_digit = cb.is_ascii_digit();
+        if !a_digit && !b_digit {
+            return bias;
+        } else if !a_digit {
+            return -1;
+        } else if !b_digit {
+            return 1;
+        } else if ca < cb {
+            if bias == 0 {
+                bias = -1;
+            }
+        } else if ca > cb && bias == 0 {
+            bias = 1;
+        }
+        *ap += 1;
+        *bp += 1;
+    }
+}
+
+/// php-src: ext/standard/strnatcmp.c `compare_left` (PHP 8.5.2)
+///
+/// Compare two left-aligned numbers: the first differing digit decides.
+fn natcmp_compare_left(a: &[u8], ap: &mut usize, b: &[u8], bp: &mut usize) -> i64 {
+    loop {
+        let ca = natcmp_at(a, *ap);
+        let cb = natcmp_at(b, *bp);
+        let a_digit = ca.is_ascii_digit();
+        let b_digit = cb.is_ascii_digit();
+        if !a_digit && !b_digit {
+            return 0;
+        } else if !a_digit {
+            return -1;
+        } else if !b_digit {
+            return 1;
+        } else if ca < cb {
+            return -1;
+        } else if ca > cb {
+            return 1;
+        }
+        *ap += 1;
+        *bp += 1;
+    }
+}