--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libzip/lib/zip_source_crc.c	Wed Jun 29 09:24:55 2016 +0200
@@ -0,0 +1,202 @@
+/*
+  zip_source_crc.c -- pass-through source that calculates CRC32 and size
+  Copyright (C) 2009-2016 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 <limits.h>
+
+#include "zipint.h"
+
+struct crc_context {
+    int validate; /* whether to check CRC on EOF and return error on mismatch */
+    int crc_complete; /* whether CRC was computed for complete file */
+    zip_error_t error;
+    zip_uint64_t size;
+    zip_uint64_t position; /* current reading position */
+    zip_uint64_t crc_position; /* how far we've computed the CRC */
+    zip_uint32_t crc;
+};
+
+static zip_int64_t crc_read(zip_source_t *, void *, void *, zip_uint64_t, zip_source_cmd_t);
+
+
+zip_source_t *
+zip_source_crc(zip_t *za, zip_source_t *src, int validate)
+{
+    struct crc_context *ctx;
+
+    if (src == NULL) {
+	zip_error_set(&za->error, ZIP_ER_INVAL, 0);
+	return NULL;
+    }
+
+    if ((ctx=(struct crc_context *)malloc(sizeof(*ctx))) == NULL) {
+	zip_error_set(&za->error, ZIP_ER_MEMORY, 0);
+	return NULL;
+    }
+
+    zip_error_init(&ctx->error);
+    ctx->validate = validate;
+    ctx->crc_complete = 0;
+    ctx->crc_position = 0;
+    ctx->crc = (zip_uint32_t)crc32(0, NULL, 0);
+    ctx->size = 0;
+
+    return zip_source_layered(za, src, crc_read, ctx);
+}
+
+
+static zip_int64_t
+crc_read(zip_source_t *src, void *_ctx, void *data, zip_uint64_t len, zip_source_cmd_t cmd)
+{
+    struct crc_context *ctx;
+    zip_int64_t n;
+
+    ctx = (struct crc_context *)_ctx;
+
+    switch (cmd) {
+        case ZIP_SOURCE_OPEN:
+            ctx->position = 0;
+            return 0;
+            
+        case ZIP_SOURCE_READ:
+            if ((n = zip_source_read(src, data, len)) < 0) {
+                _zip_error_set_from_source(&ctx->error, src);
+                return -1;
+            }
+            
+            if (n == 0) {
+                if (ctx->crc_position == ctx->position) {
+                    ctx->crc_complete = 1;
+                    ctx->size = ctx->position;
+
+                    if (ctx->validate) {
+                        struct zip_stat st;
+                    
+                        if (zip_source_stat(src, &st) < 0) {
+                            _zip_error_set_from_source(&ctx->error, src);
+                            return -1;
+                        }
+                    
+                        if ((st.valid & ZIP_STAT_CRC) && st.crc != ctx->crc) {
+                            zip_error_set(&ctx->error, ZIP_ER_CRC, 0);
+                            return -1;
+                        }
+                        if ((st.valid & ZIP_STAT_SIZE) && st.size != ctx->size) {
+                            zip_error_set(&ctx->error, ZIP_ER_INCONS, 0);
+                            return -1;
+                        }
+                    }
+                }
+            }
+            else if (!ctx->crc_complete && ctx->position <= ctx->crc_position) {
+		zip_uint64_t i, nn;
+
+		for (i = ctx->crc_position - ctx->position; i < (zip_uint64_t)n; i += nn) {
+		    nn = ZIP_MIN(UINT_MAX, (zip_uint64_t)n-i);
+
+		    ctx->crc = (zip_uint32_t)crc32(ctx->crc, (const Bytef *)data+i, (uInt)nn);
+                    ctx->crc_position += nn;
+		}
+            }
+            ctx->position += (zip_uint64_t)n;
+            return n;
+
+        case ZIP_SOURCE_CLOSE:
+            return 0;
+
+        case ZIP_SOURCE_STAT:
+        {
+            zip_stat_t *st;
+
+	    st = (zip_stat_t *)data;
+
+	    if (ctx->crc_complete) {
+		/* TODO: Set comp_size, comp_method, encryption_method?
+		        After all, this only works for uncompressed data. */
+		st->size = ctx->size;
+		st->crc = ctx->crc;
+		st->comp_size = ctx->size;
+		st->comp_method = ZIP_CM_STORE;
+		st->encryption_method = ZIP_EM_NONE;
+		st->valid |= ZIP_STAT_SIZE|ZIP_STAT_CRC|ZIP_STAT_COMP_SIZE|ZIP_STAT_COMP_METHOD|ZIP_STAT_ENCRYPTION_METHOD;;
+	    }
+            return 0;
+        }
+            
+        case ZIP_SOURCE_ERROR:
+            return zip_error_to_data(&ctx->error, data, len);
+
+        case ZIP_SOURCE_FREE:
+            free(ctx);
+            return 0;
+            
+        case ZIP_SOURCE_SUPPORTS:
+        {
+            zip_int64_t mask = zip_source_supports(src);
+
+            if (mask < 0) {
+                _zip_error_set_from_source(&ctx->error, src);
+                return -1;
+            }
+
+            return mask & ~zip_source_make_command_bitmap(ZIP_SOURCE_BEGIN_WRITE, ZIP_SOURCE_COMMIT_WRITE, ZIP_SOURCE_ROLLBACK_WRITE, ZIP_SOURCE_SEEK_WRITE, ZIP_SOURCE_TELL_WRITE, ZIP_SOURCE_REMOVE, -1);
+        }
+
+        case ZIP_SOURCE_SEEK:
+        {
+            zip_int64_t new_position;
+            zip_source_args_seek_t *args = ZIP_SOURCE_GET_ARGS(zip_source_args_seek_t, data, len, &ctx->error);
+
+	    if (args == NULL) {
+		return -1;
+	    }
+            if (zip_source_seek(src, args->offset, args->whence) < 0 || (new_position = zip_source_tell(src)) < 0) {
+                _zip_error_set_from_source(&ctx->error, src);
+                return -1;
+            }
+
+            ctx->position = (zip_uint64_t)new_position;
+
+            return 0;
+        }
+
+        case ZIP_SOURCE_TELL:
+            return (zip_int64_t)ctx->position;
+            
+        default:
+            zip_error_set(&ctx->error, ZIP_ER_OPNOTSUPP, 0);
+            return -1;
+    }
+}