From 465e7c27e032c7999d58be13a5574493a3f6573e Mon Sep 17 00:00:00 2001
From: Chris Hanson <org/chris-hanson/cph>
Date: Wed, 26 Apr 2017 00:34:04 -0700
Subject: [PATCH] Implement named char codecs.

---
 src/runtime/char.scm    | 94 ++++++++++++++++++++++++++++++++++++++++-
 src/runtime/runtime.pkg |  4 ++
 2 files changed, 97 insertions(+), 1 deletion(-)

diff --git a/src/runtime/char.scm b/src/runtime/char.scm
index f1c6a23ca..78371080e 100644
--- a/src/runtime/char.scm
+++ b/src/runtime/char.scm
@@ -509,6 +509,10 @@ USA.
 	((utf8-initial-byte-4? b0) 4)
 	(else (error "Illegal UTF-8 initial byte:" b0))))
 
+(define (next-char-length:utf8 bv bs be)
+  (and (fix:<= (fix:+ bs 1) be)
+       (initial-byte->utf8-char-length (bytevector-u8-ref bv bs))))
+
 (define (decode-utf8-char bytes index)
   (integer->char
    (let ((b0 (bytevector-u8-ref bytes index)))
@@ -618,6 +622,14 @@ USA.
       4
       2))
 
+(define (next-char-length:utf16le bv bs be)
+  (and (fix:<= (fix:+ bs 2) be)
+       (initial-u16->utf16-char-length (bytevector-u16le-ref bv bs))))
+
+(define (next-char-length:utf16be bv bs be)
+  (and (fix:<= (fix:+ bs 2) be)
+       (initial-u16->utf16-char-length (bytevector-u16be-ref bv bs))))
+
 (define (utf16-char-decoder getter)
   (lambda (bytes index)
     (integer->char
@@ -643,6 +655,14 @@ USA.
   (guarantee unicode-scalar-value? u32 'initial-u32->utf32-char-length)
   4)
 
+(define (next-char-length:utf32le bv bs be)
+  (and (fix:<= (fix:+ bs 2) be)
+       (initial-u32->utf32-char-length (bytevector-u32le-ref bv bs))))
+
+(define (next-char-length:utf32be bv bs be)
+  (and (fix:<= (fix:+ bs 2) be)
+       (initial-u32->utf32-char-length (bytevector-u32be-ref bv bs))))
+
 (define (utf32-char-decoder getter)
   (lambda (bytes index)
     (let ((u32 (getter bytes index)))
@@ -653,4 +673,76 @@ USA.
   (utf32-char-decoder bytevector-u32be-ref))
 
 (define decode-utf32le-char
-  (utf32-char-decoder bytevector-u32le-ref))
\ No newline at end of file
+  (utf32-char-decoder bytevector-u32le-ref))
+
+;;;; Codecs
+
+(define-record-type <char-codec>
+    (make-char-codec encoder decoder)
+    char-codec?
+  (encoder char-codec-encoder)
+  (decoder char-codec-decoder))
+
+(define get-char-codec)
+(define set-char-codec!)
+(add-boot-init!
+ (lambda ()
+   (let ((table (make-alist-metadata-table)))
+     (set! get-char-codec (table 'get))
+     (set! set-char-codec! (table 'put!))
+     unspecific)))
+
+(define (define-char-codec name codec)
+  (add-boot-init! (lambda () (set-char-codec! name codec))))
+
+(define (unicode-codec char-byte-length encode-char!
+		       next-char-length decode-char)
+  (make-char-codec
+   (lambda (bv bs be char)
+     (let ((bs* (fix:+ bs (char-byte-length char))))
+       (and (fix:<= bs* be)
+	    (begin
+	      (encode-char! bv bs char)
+	      bs*))))
+   (lambda (bv bs be k)
+     (let ((n (next-char-length bv bs be)))
+       (if (not n)
+	   (k #f bs)
+	   (let ((bs* (fix:+ bs n)))
+	     (k (and (fix:<= bs* be)
+		     (decode-char bv bs))
+		bs*)))))))
+
+(define-char-codec 'utf8
+  (unicode-codec char-utf8-byte-length encode-utf8-char!
+		 next-char-length:utf8 decode-utf8-char))
+
+(define-char-codec 'utf16le
+  (unicode-codec char-utf16-byte-length encode-utf16le-char!
+		 next-char-length:utf16le decode-utf16le-char))
+
+(define-char-codec 'utf16be
+  (unicode-codec char-utf16-byte-length encode-utf16be-char!
+		 next-char-length:utf16be decode-utf16be-char))
+
+(define-char-codec 'utf32le
+  (unicode-codec char-utf32-byte-length encode-utf32le-char!
+		 next-char-length:utf32le decode-utf32le-char))
+
+(define-char-codec 'utf32be
+  (unicode-codec char-utf32-byte-length encode-utf32be-char!
+		 next-char-length:utf32be decode-utf32be-char))
+
+(define-char-codec 'iso-8859-1
+  (make-char-codec
+   (lambda (bv bs be char)
+     (let ((bs* (fix:+ bs 1)))
+       (and (fix:<= bs* be)
+	    (begin
+	      (bytevector-u8-set! bv bs (char->integer char))
+	      bs*))))
+   (lambda (bv bs be k)
+     (let ((bs* (fix:+ bs 1)))
+       (k (and (fix:<= bs* be)
+	       (integer->char (bytevector-u8-ref bv bs)))
+	  bs*)))))
\ No newline at end of file
diff --git a/src/runtime/runtime.pkg b/src/runtime/runtime.pkg
index 9e3ec659f..d160f1dc8 100644
--- a/src/runtime/runtime.pkg
+++ b/src/runtime/runtime.pkg
@@ -1216,6 +1216,9 @@ USA.
 	  char-ci>?
 	  char-code
 	  char-code-limit
+	  char-codec-decoder
+	  char-codec-encoder
+	  char-codec?
 	  char-downcase
 	  char-foldcase
 	  char-general-category
@@ -1232,6 +1235,7 @@ USA.
 	  decode-utf8-char
 	  digit->char
 	  digit-value
+	  get-char-codec
 	  integer->char
 	  make-char
 	  name->char
-- 
2.25.1