Improve internal data structures.  New extra field API (read only).
Added paranoid mode to zipcmp (compare more meta data).

Keep up-to-date metadata for changed entries, avoid parallel arrays.
XXX: Modifying extra fields API functions are stubs.  Old API removed.

lib/zip_string.c

diff --git a/lib/zip_string.c b/lib/zip_string.c
new file mode 100644
index 0000000..b837ea8
--- /dev/null
+++ b/lib/zip_string.c
@@ -0,0 +1,157 @@
+/*
+  zip_string.c -- string handling (with encoding)
+  Copyright (C) 2012 Dieter Baron and Thomas Klausner
+
+  This file is part of libzip, a library to manipulate ZIP archives.
+  The authors can be contacted at <libzip@nih.at>
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions
+  are met:
+  1. Redistributions of source code must retain the above copyright
+     notice, this list of conditions and the following disclaimer.
+  2. Redistributions in binary form must reproduce the above copyright
+     notice, this list of conditions and the following disclaimer in
+     the documentation and/or other materials provided with the
+     distribution.
+  3. The names of the authors may not be used to endorse or promote
+     products derived from this software without specific prior
+     written permission.
+ 
+  THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS
+  OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+  ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
+  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
+  GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
+  IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+  OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
+  IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "zipint.h"
+
+
+
+int
+_zip_string_equal(const struct zip_string *a, const struct zip_string *b)
+{
+    if (a == NULL || b == NULL)
+	return a == b;
+
+    if (a->length != b->length)
+	return 0;
+
+    /* XXX: encoding */
+
+    return (memcmp(a->raw, b->raw, a->length) == 0);
+}
+
+
+
+void
+_zip_string_free(struct zip_string *s)
+{
+    if (s == NULL)
+	return;
+
+    free(s->raw);
+    free(s->converted);
+    free(s);
+}
+
+
+
+const zip_uint8_t *
+_zip_string_get(struct zip_string *string, zip_uint32_t *lenp, int flags, struct zip_error *error)
+{
+    static const zip_uint8_t empty[1] = "";
+
+    if (string == NULL) {
+	if (lenp)
+	    *lenp = 0;
+	return empty;
+    }
+
+    if ((flags & ZIP_FL_NAME_RAW) == 0) {
+	/* start guessing */
+	if (string->encoding == ZIP_ENCODING_UNKNOWN)
+	    _zip_guess_encoding(string, ZIP_ENCODING_UNKNOWN);
+
+	if (((flags & ZIP_FL_NAME_STRICT)
+	     && string->encoding != ZIP_ENCODING_ASCII && string->encoding != ZIP_ENCODING_UTF8_KNOWN)
+	    || (string->encoding == ZIP_ENCODING_CP437)) {
+	    if (string->converted == NULL) {
+		if ((string->converted=_zip_cp437_to_utf8(string->raw, string->length,
+							  &string->converted_length, error)) == NULL)
+		    return NULL;
+	    }
+	    if (lenp)
+		*lenp = string->converted_length;
+	    return string->converted;
+	}
+    }
+    
+    if (lenp)
+	*lenp = string->length;
+    return string->raw;
+}
+
+
+
+zip_uint16_t
+_zip_string_length(const struct zip_string *s)
+{
+    if (s == NULL)
+	return 0;
+
+    return s->length;
+}
+
+
+
+struct zip_string *
+_zip_string_new(const zip_uint8_t *raw, zip_uint16_t length, struct zip_error *error)
+{
+    struct zip_string *s;
+    
+    if (length == 0)
+	return NULL;
+
+    if ((s=malloc(sizeof(*s))) == NULL) {
+	_zip_error_set(error, ZIP_ER_MEMORY, 0);
+	return NULL;
+    }
+
+    if ((s->raw=malloc(length+1)) == NULL) {
+	free(s);
+	return NULL;
+    }
+
+    memcpy(s->raw, raw, length);
+    s->raw[length] = '\0';
+    s->length = length;
+    s->encoding = ZIP_ENCODING_UNKNOWN;
+    s->converted = NULL;
+    s->converted_length = 0;
+
+    return s;
+}
+
+
+
+void
+_zip_string_write(const struct zip_string *s, FILE *f)
+{
+    if (s == NULL)
+	return;
+    
+    fwrite(s->raw, s->length, 1, f);
+}