1 files changed, 477 insertions, 267 deletions
diff --git a/src/Common/libzip/zip_source_buffer.c b/src/Common/libzip/zip_source_buffer.c
index f3f8ee0d..44159536 100644
--- a/src/Common/libzip/zip_source_buffer.c
+++ b/src/Common/libzip/zip_source_buffer.c
@@ -1,9 +1,9 @@
 /*
   zip_source_buffer.c -- create zip data source from buffer
-  Copyright (C) 1999-2016 Dieter Baron and Thomas Klausner
+  Copyright (C) 1999-2022 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>
+  The authors can be contacted at <info@libzip.org>
 
   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
@@ -17,7 +17,7 @@
   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
@@ -37,18 +37,23 @@
 #include "zipint.h"
 
 #ifndef WRITE_FRAGMENT_SIZE
-#define WRITE_FRAGMENT_SIZE 64*1024
+#define WRITE_FRAGMENT_SIZE (64 * 1024)
 #endif
 
 struct buffer {
-    zip_uint64_t fragment_size;		/* size of each fragment */
-
-    zip_uint8_t **fragments;		/* pointers to fragments */
-    zip_uint64_t nfragments;		/* number of allocated fragments */
-    zip_uint64_t fragments_capacity;	/* size of fragments (number of pointers) */
-    zip_uint64_t size;			/* size of data in bytes */
-    zip_uint64_t offset;		/* current offset */
-    int free_data;
+    zip_buffer_fragment_t *fragments; /* fragments */
+    zip_uint64_t *fragment_offsets;   /* offset of each fragment from start of buffer, nfragments+1 entries */
+    zip_uint64_t nfragments;          /* number of allocated fragments */
+    zip_uint64_t fragments_capacity;  /* size of fragments (number of pointers) */
+
+    zip_uint64_t first_owned_fragment; /* first fragment to free data from */
+
+    zip_uint64_t shared_fragments; /* number of shared fragments */
+    struct buffer *shared_buffer;  /* buffer fragments are shared with */
+
+    zip_uint64_t size;             /* size of buffer */
+    zip_uint64_t offset;           /* current offset in buffer */
+    zip_uint64_t current_fragment; /* fragment current offset is in */
 };
 
 typedef struct buffer buffer_t;
@@ -56,380 +61,585 @@ typedef struct buffer buffer_t;
 struct read_data {
     zip_error_t error;
     time_t mtime;
+    zip_file_attributes_t attributes;
     buffer_t *in;
     buffer_t *out;
 };
 
+#define buffer_capacity(buffer) ((buffer)->fragment_offsets[(buffer)->nfragments])
+#define buffer_size(buffer) ((buffer)->size)
+
+static buffer_t *buffer_clone(buffer_t *buffer, zip_uint64_t length, zip_error_t *error);
+static zip_uint64_t buffer_find_fragment(const buffer_t *buffer, zip_uint64_t offset);
 static void buffer_free(buffer_t *buffer);
-static buffer_t *buffer_new(zip_uint64_t fragment_size);
-static buffer_t *buffer_new_read(const void *data, zip_uint64_t length, int free_data);
-static buffer_t *buffer_new_write(zip_uint64_t fragment_size);
+static bool buffer_grow_fragments(buffer_t *buffer, zip_uint64_t capacity, zip_error_t *error);
+static buffer_t *buffer_new(const zip_buffer_fragment_t *fragments, zip_uint64_t nfragments, int free_data, zip_error_t *error);
 static zip_int64_t buffer_read(buffer_t *buffer, zip_uint8_t *data, zip_uint64_t length);
 static int buffer_seek(buffer_t *buffer, void *data, zip_uint64_t len, zip_error_t *error);
 static zip_int64_t buffer_write(buffer_t *buffer, const zip_uint8_t *data, zip_uint64_t length, zip_error_t *);
 
 static zip_int64_t read_data(void *, void *, zip_uint64_t, zip_source_cmd_t);
 
+zip_source_t *zip_source_buffer_with_attributes_create(const void *data, zip_uint64_t len, int freep, zip_file_attributes_t *attributes, zip_error_t *error);
+zip_source_t *zip_source_buffer_fragment_with_attributes_create(const zip_buffer_fragment_t *fragments, zip_uint64_t nfragments, int freep, zip_file_attributes_t *attributes, zip_error_t *error);
+
 
 ZIP_EXTERN zip_source_t *
-zip_source_buffer(zip_t *za, const void *data, zip_uint64_t len, int freep)
-{
+zip_source_buffer(zip_t *za, const void *data, zip_uint64_t len, int freep) {
     if (za == NULL)
-	return NULL;
+        return NULL;
+
+    return zip_source_buffer_with_attributes_create(data, len, freep, NULL, &za->error);
+}
+
+
+ZIP_EXTERN zip_source_t *
+zip_source_buffer_create(const void *data, zip_uint64_t len, int freep, zip_error_t *error) {
+    return zip_source_buffer_with_attributes_create(data, len, freep, NULL, error);
+}
+
+
+zip_source_t *
+zip_source_buffer_with_attributes_create(const void *data, zip_uint64_t len, int freep, zip_file_attributes_t *attributes, zip_error_t *error) {
+    zip_buffer_fragment_t fragment;
+
+    if (data == NULL) {
+        if (len > 0) {
+            zip_error_set(error, ZIP_ER_INVAL, 0);
+            return NULL;
+        }
+
+        return zip_source_buffer_fragment_with_attributes_create(NULL, 0, freep, attributes, error);
+    }
+
+    fragment.data = (zip_uint8_t *)data;
+    fragment.length = len;
 
-    return zip_source_buffer_create(data, len, freep, &za->error);
+    return zip_source_buffer_fragment_with_attributes_create(&fragment, 1, freep, attributes, error);
 }
 
 
 ZIP_EXTERN zip_source_t *
-zip_source_buffer_create(const void *data, zip_uint64_t len, int freep, zip_error_t *error)
-{
+zip_source_buffer_fragment(zip_t *za, const zip_buffer_fragment_t *fragments, zip_uint64_t nfragments, int freep) {
+    if (za == NULL) {
+        return NULL;
+    }
+
+    return zip_source_buffer_fragment_with_attributes_create(fragments, nfragments, freep, NULL, &za->error);
+}
+
+
+ZIP_EXTERN zip_source_t *
+zip_source_buffer_fragment_create(const zip_buffer_fragment_t *fragments, zip_uint64_t nfragments, int freep, zip_error_t *error) {
+    return zip_source_buffer_fragment_with_attributes_create(fragments, nfragments, freep, NULL, error);
+}
+
+zip_source_t *
+zip_source_buffer_fragment_with_attributes_create(const zip_buffer_fragment_t *fragments, zip_uint64_t nfragments, int freep, zip_file_attributes_t *attributes, zip_error_t *error) {
     struct read_data *ctx;
     zip_source_t *zs;
+    buffer_t *buffer;
 
-    if (data == NULL && len > 0) {
-	zip_error_set(error, ZIP_ER_INVAL, 0);
-	return NULL;
+    if (fragments == NULL && nfragments > 0) {
+        zip_error_set(error, ZIP_ER_INVAL, 0);
+        return NULL;
     }
 
-    if ((ctx=(struct read_data *)malloc(sizeof(*ctx))) == NULL) {
-	zip_error_set(error, ZIP_ER_MEMORY, 0);
-	return NULL;
+    if ((buffer = buffer_new(fragments, nfragments, freep, error)) == NULL) {
+        return NULL;
     }
 
-    if ((ctx->in = buffer_new_read(data, len, freep)) == NULL) {
-	zip_error_set(error, ZIP_ER_MEMORY, 0);
-	free(ctx);
-	return NULL;
+    if ((ctx = (struct read_data *)malloc(sizeof(*ctx))) == NULL) {
+        zip_error_set(error, ZIP_ER_MEMORY, 0);
+        buffer_free(buffer);
+        return NULL;
     }
 
+    ctx->in = buffer;
     ctx->out = NULL;
     ctx->mtime = time(NULL);
+    if (attributes) {
+        (void)memcpy_s(&ctx->attributes, sizeof(ctx->attributes), attributes, sizeof(ctx->attributes));
+    }
+    else {
+        zip_file_attributes_init(&ctx->attributes);
+    }
     zip_error_init(&ctx->error);
-    
-    if ((zs=zip_source_function_create(read_data, ctx, error)) == NULL) {
-	buffer_free(ctx->in);
-	free(ctx);
-	return NULL;
+
+    if ((zs = zip_source_function_create(read_data, ctx, error)) == NULL) {
+        buffer_free(ctx->in);
+        free(ctx);
+        return NULL;
     }
 
     return zs;
 }
 
 
+zip_source_t *
+zip_source_buffer_with_attributes(zip_t *za, const void *data, zip_uint64_t len, int freep, zip_file_attributes_t *attributes) {
+    return zip_source_buffer_with_attributes_create(data, len, freep, attributes, &za->error);
+}
+
 static zip_int64_t
-read_data(void *state, void *data, zip_uint64_t len, zip_source_cmd_t cmd)
-{
+read_data(void *state, void *data, zip_uint64_t len, zip_source_cmd_t cmd) {
     struct read_data *ctx = (struct read_data *)state;
 
     switch (cmd) {
-        case ZIP_SOURCE_BEGIN_WRITE:
-	    if ((ctx->out = buffer_new_write(WRITE_FRAGMENT_SIZE)) == NULL) {
-		zip_error_set(&ctx->error, ZIP_ER_MEMORY, 0);
-		return -1;
-	    }
-	    return 0;
-
-        case ZIP_SOURCE_CLOSE:
-            return 0;
-            
-        case ZIP_SOURCE_COMMIT_WRITE:
-	    buffer_free(ctx->in);
-	    ctx->in = ctx->out;
-	    ctx->out = NULL;
-	    return 0;
-
-        case ZIP_SOURCE_ERROR:
-            return zip_error_to_data(&ctx->error, data, len);
-            
-        case ZIP_SOURCE_FREE:
-	    buffer_free(ctx->in);
-	    buffer_free(ctx->out);
-            free(ctx);
-            return 0;
-            
-        case ZIP_SOURCE_OPEN:
-	    ctx->in->offset = 0;
-            return 0;
-	
-        case ZIP_SOURCE_READ:
-	    if (len > ZIP_INT64_MAX) {
-		zip_error_set(&ctx->error, ZIP_ER_INVAL, 0);
-		return -1;
-	    }
-            return buffer_read(ctx->in, data, len);
-	
-        case ZIP_SOURCE_REMOVE:
-	{
-	    buffer_t *empty = buffer_new_read(NULL, 0, 0);
-	    if (empty == 0) {
-		zip_error_set(&ctx->error, ZIP_ER_MEMORY, 0);
-		return -1;
-	    }
-	
-	    buffer_free(ctx->in);
-	    ctx->in = empty;
-	    return 0;
-	}
-
-        case ZIP_SOURCE_ROLLBACK_WRITE:
-	    buffer_free(ctx->out);
-	    ctx->out = NULL;
-	    return 0;
-
-        case ZIP_SOURCE_SEEK:
-	    return buffer_seek(ctx->in, data, len, &ctx->error);
-
-        case ZIP_SOURCE_SEEK_WRITE:
-	    return buffer_seek(ctx->out, data, len, &ctx->error);
-       
-        case ZIP_SOURCE_STAT:
-        {
-            zip_stat_t *st;
-	    
-	    if (len < sizeof(*st)) {
-                zip_error_set(&ctx->error, ZIP_ER_INVAL, 0);
-		return -1;
-	    }
-
-	    st = (zip_stat_t *)data;
-
-	    zip_stat_init(st);
-	    st->mtime = ctx->mtime;
-	    st->size = ctx->in->size;
-	    st->comp_size = st->size;
-	    st->comp_method = ZIP_CM_STORE;
-	    st->encryption_method = ZIP_EM_NONE;
-	    st->valid = ZIP_STAT_MTIME|ZIP_STAT_SIZE|ZIP_STAT_COMP_SIZE|ZIP_STAT_COMP_METHOD|ZIP_STAT_ENCRYPTION_METHOD;
-	    
-	    return sizeof(*st);
-	}
-
-        case ZIP_SOURCE_SUPPORTS:
-	    return zip_source_make_command_bitmap(ZIP_SOURCE_OPEN, ZIP_SOURCE_READ, ZIP_SOURCE_CLOSE, ZIP_SOURCE_STAT, ZIP_SOURCE_ERROR, ZIP_SOURCE_FREE, ZIP_SOURCE_SEEK, ZIP_SOURCE_TELL, ZIP_SOURCE_BEGIN_WRITE, ZIP_SOURCE_COMMIT_WRITE, ZIP_SOURCE_REMOVE, ZIP_SOURCE_ROLLBACK_WRITE, ZIP_SOURCE_SEEK_WRITE, ZIP_SOURCE_TELL_WRITE, ZIP_SOURCE_WRITE, -1);
-            
-        case ZIP_SOURCE_TELL:
-            if (ctx->in->offset > ZIP_INT64_MAX) {
-		zip_error_set(&ctx->error, ZIP_ER_TELL, EOVERFLOW);
-		return -1;
-	    }
-	    return (zip_int64_t)ctx->in->offset;
-		
-            
-        case ZIP_SOURCE_TELL_WRITE:
-            if (ctx->out->offset > ZIP_INT64_MAX) {
-		zip_error_set(&ctx->error, ZIP_ER_TELL, EOVERFLOW);
-		return -1;
-	    }
-	    return (zip_int64_t)ctx->out->offset;
-
-        case ZIP_SOURCE_WRITE:
-	    if (len > ZIP_INT64_MAX) {
-		zip_error_set(&ctx->error, ZIP_ER_INVAL, 0);
-		return -1;
-	    }
-	    return buffer_write(ctx->out, data, len, &ctx->error);
-
-        default:
-	    zip_error_set(&ctx->error, ZIP_ER_OPNOTSUPP, 0);
+    case ZIP_SOURCE_BEGIN_WRITE:
+        if ((ctx->out = buffer_new(NULL, 0, 0, &ctx->error)) == NULL) {
+            return -1;
+        }
+        ctx->out->offset = 0;
+        ctx->out->current_fragment = 0;
+        return 0;
+
+    case ZIP_SOURCE_BEGIN_WRITE_CLONING:
+        if ((ctx->out = buffer_clone(ctx->in, len, &ctx->error)) == NULL) {
             return -1;
+        }
+        ctx->out->offset = len;
+        ctx->out->current_fragment = ctx->out->nfragments;
+        return 0;
+
+    case ZIP_SOURCE_CLOSE:
+        return 0;
+
+    case ZIP_SOURCE_COMMIT_WRITE:
+        buffer_free(ctx->in);
+        ctx->in = ctx->out;
+        ctx->out = NULL;
+        return 0;
+
+    case ZIP_SOURCE_ERROR:
+        return zip_error_to_data(&ctx->error, data, len);
+
+    case ZIP_SOURCE_FREE:
+        buffer_free(ctx->in);
+        buffer_free(ctx->out);
+        free(ctx);
+        return 0;
+
+    case ZIP_SOURCE_GET_FILE_ATTRIBUTES: {
+        if (len < sizeof(ctx->attributes)) {
+            zip_error_set(&ctx->error, ZIP_ER_INVAL, 0);
+            return -1;
+        }
+
+        (void)memcpy_s(data, sizeof(ctx->attributes), &ctx->attributes, sizeof(ctx->attributes));
+
+        return sizeof(ctx->attributes);
     }
-}
 
+    case ZIP_SOURCE_OPEN:
+        ctx->in->offset = 0;
+        ctx->in->current_fragment = 0;
+        return 0;
 
-static void
-buffer_free(buffer_t *buffer)
-{
-    if (buffer == NULL) {
-	return; 
+    case ZIP_SOURCE_READ:
+        if (len > ZIP_INT64_MAX) {
+            zip_error_set(&ctx->error, ZIP_ER_INVAL, 0);
+            return -1;
+        }
+        return buffer_read(ctx->in, data, len);
+
+    case ZIP_SOURCE_REMOVE: {
+        buffer_t *empty = buffer_new(NULL, 0, 0, &ctx->error);
+        if (empty == NULL) {
+            return -1;
+        }
+
+        buffer_free(ctx->in);
+        ctx->in = empty;
+        return 0;
     }
 
-    if (buffer->free_data) {
-	zip_uint64_t i;
+    case ZIP_SOURCE_ROLLBACK_WRITE:
+        buffer_free(ctx->out);
+        ctx->out = NULL;
+        return 0;
+
+    case ZIP_SOURCE_SEEK:
+        return buffer_seek(ctx->in, data, len, &ctx->error);
+
+    case ZIP_SOURCE_SEEK_WRITE:
+        return buffer_seek(ctx->out, data, len, &ctx->error);
 
-	for (i=0; i < buffer->nfragments; i++) {
-	    free(buffer->fragments[i]);
-	}
+    case ZIP_SOURCE_STAT: {
+        zip_stat_t *st;
+
+        if (len < sizeof(*st)) {
+            zip_error_set(&ctx->error, ZIP_ER_INVAL, 0);
+            return -1;
+        }
+
+        st = (zip_stat_t *)data;
+
+        zip_stat_init(st);
+        st->mtime = ctx->mtime;
+        st->size = ctx->in->size;
+        st->comp_size = st->size;
+        st->comp_method = ZIP_CM_STORE;
+        st->encryption_method = ZIP_EM_NONE;
+        st->valid = ZIP_STAT_MTIME | ZIP_STAT_SIZE | ZIP_STAT_COMP_SIZE | ZIP_STAT_COMP_METHOD | ZIP_STAT_ENCRYPTION_METHOD;
+
+        return sizeof(*st);
+    }
+
+    case ZIP_SOURCE_SUPPORTS:
+        return zip_source_make_command_bitmap(ZIP_SOURCE_GET_FILE_ATTRIBUTES, ZIP_SOURCE_OPEN, ZIP_SOURCE_READ, ZIP_SOURCE_CLOSE, ZIP_SOURCE_STAT, ZIP_SOURCE_ERROR, ZIP_SOURCE_FREE, ZIP_SOURCE_SEEK, ZIP_SOURCE_TELL, ZIP_SOURCE_BEGIN_WRITE, ZIP_SOURCE_BEGIN_WRITE_CLONING, ZIP_SOURCE_COMMIT_WRITE, ZIP_SOURCE_REMOVE, ZIP_SOURCE_ROLLBACK_WRITE, ZIP_SOURCE_SEEK_WRITE, ZIP_SOURCE_TELL_WRITE, ZIP_SOURCE_WRITE, ZIP_SOURCE_SUPPORTS_REOPEN, -1);
+
+    case ZIP_SOURCE_TELL:
+        if (ctx->in->offset > ZIP_INT64_MAX) {
+            zip_error_set(&ctx->error, ZIP_ER_TELL, EOVERFLOW);
+            return -1;
+        }
+        return (zip_int64_t)ctx->in->offset;
+
+
+    case ZIP_SOURCE_TELL_WRITE:
+        if (ctx->out->offset > ZIP_INT64_MAX) {
+            zip_error_set(&ctx->error, ZIP_ER_TELL, EOVERFLOW);
+            return -1;
+        }
+        return (zip_int64_t)ctx->out->offset;
+
+    case ZIP_SOURCE_WRITE:
+        if (len > ZIP_INT64_MAX) {
+            zip_error_set(&ctx->error, ZIP_ER_INVAL, 0);
+            return -1;
+        }
+        return buffer_write(ctx->out, data, len, &ctx->error);
+
+    default:
+        zip_error_set(&ctx->error, ZIP_ER_OPNOTSUPP, 0);
+        return -1;
     }
-    free(buffer->fragments);
-    free(buffer);
 }
 
 
 static buffer_t *
-buffer_new(zip_uint64_t fragment_size)
-{
-    buffer_t *buffer;
+buffer_clone(buffer_t *buffer, zip_uint64_t offset, zip_error_t *error) {
+    zip_uint64_t fragment, fragment_offset, waste;
+    buffer_t *clone;
 
-    if ((buffer = malloc(sizeof(*buffer))) == NULL) {
-	return NULL;
+    if (offset == 0) {
+        return buffer_new(NULL, 0, 1, error);
     }
 
-    buffer->fragment_size = fragment_size;
-    buffer->offset = 0;
-    buffer->free_data = 0;
-    buffer->nfragments = 0;
-    buffer->fragments_capacity = 0;
-    buffer->fragments = NULL;
-    buffer->size = 0;
+    if (offset > buffer->size) {
+        zip_error_set(error, ZIP_ER_INVAL, 0);
+        return NULL;
+    }
+    if (buffer->shared_buffer != NULL) {
+        zip_error_set(error, ZIP_ER_INUSE, 0);
+        return NULL;
+    }
 
-    return buffer;
+    fragment = buffer_find_fragment(buffer, offset);
+    fragment_offset = offset - buffer->fragment_offsets[fragment];
+
+    if (fragment_offset == 0) {
+        fragment--;
+        fragment_offset = buffer->fragments[fragment].length;
+    }
+
+    /* TODO: This should also consider the length of the fully shared fragments */
+    waste = buffer->fragments[fragment].length - fragment_offset;
+    if (waste > offset) {
+        zip_error_set(error, ZIP_ER_OPNOTSUPP, 0);
+        return NULL;
+    }
+
+    if ((clone = buffer_new(buffer->fragments, fragment + 1, 0, error)) == NULL) {
+        return NULL;
+    }
+
+#ifndef __clang_analyzer__
+    /* clone->fragments can't be null, since it was created with at least one fragment */
+    clone->fragments[fragment].length = fragment_offset;
+#endif
+    clone->fragment_offsets[clone->nfragments] = offset;
+    clone->size = offset;
+
+    clone->first_owned_fragment = ZIP_MIN(buffer->first_owned_fragment, clone->nfragments);
+
+    buffer->shared_buffer = clone;
+    clone->shared_buffer = buffer;
+    buffer->shared_fragments = fragment + 1;
+    clone->shared_fragments = fragment + 1;
+    
+    return clone;
 }
 
 
-static buffer_t *
-buffer_new_read(const void *data, zip_uint64_t length, int free_data)
-{
-    buffer_t *buffer;
+static zip_uint64_t
+buffer_find_fragment(const buffer_t *buffer, zip_uint64_t offset) {
+    zip_uint64_t low, high, mid;
 
-    if ((buffer = buffer_new(length)) == NULL) {
-	return NULL;
+    if (buffer->nfragments == 0) {
+        return 0;
     }
 
-    buffer->size = length;
+    low = 0;
+    high = buffer->nfragments - 1;
+
+    while (low < high) {
+        mid = (high - low) / 2 + low;
+        if (buffer->fragment_offsets[mid] > offset) {
+            high = mid - 1;
+        }
+        else if (mid == buffer->nfragments || buffer->fragment_offsets[mid + 1] > offset) {
+            return mid;
+        }
+        else {
+            low = mid + 1;
+        }
+    }
+
+    return low;
+}
 
-    if (length > 0) {
-	if ((buffer->fragments = malloc(sizeof(*(buffer->fragments)))) == NULL) {
-	    buffer_free(buffer);
-	    return NULL;
-	}
-	buffer->fragments_capacity = 1;
 
-	buffer->nfragments = 1;
-	buffer->fragments[0] = (zip_uint8_t *)data;
-	buffer->free_data = free_data;
+static void
+buffer_free(buffer_t *buffer) {
+    zip_uint64_t i;
+
+    if (buffer == NULL) {
+        return;
     }
 
-    return buffer;
+    if (buffer->shared_buffer != NULL) {
+        buffer->shared_buffer->shared_buffer = NULL;
+        buffer->shared_buffer->shared_fragments = 0;
+
+        buffer->first_owned_fragment = ZIP_MAX(buffer->first_owned_fragment, buffer->shared_fragments);
+    }
+
+    for (i = buffer->first_owned_fragment; i < buffer->nfragments; i++) {
+        free(buffer->fragments[i].data);
+    }
+    free(buffer->fragments);
+    free(buffer->fragment_offsets);
+    free(buffer);
+}
+
+
+static bool
+buffer_grow_fragments(buffer_t *buffer, zip_uint64_t capacity, zip_error_t *error) {
+    zip_buffer_fragment_t *fragments;
+    zip_uint64_t *offsets;
+    zip_uint64_t fragments_size;
+    zip_uint64_t offsets_size;
+
+    if (capacity < buffer->fragments_capacity) {
+        return true;
+    }
+
+    fragments_size = sizeof(buffer->fragments[0]) * capacity;
+    offsets_size = sizeof(buffer->fragment_offsets[0]) * (capacity + 1);
+
+    if (capacity == ZIP_UINT64_MAX || fragments_size < capacity || fragments_size > SIZE_MAX|| offsets_size < capacity || offsets_size > SIZE_MAX) {
+        zip_error_set(error, ZIP_ER_MEMORY, 0);
+        return false;
+    }
+
+    if ((fragments = realloc(buffer->fragments, (size_t)fragments_size)) == NULL) {
+        zip_error_set(error, ZIP_ER_MEMORY, 0);
+        return false;
+    }
+    buffer->fragments = fragments;
+    if ((offsets = realloc(buffer->fragment_offsets, (size_t)offsets_size)) == NULL) {
+        zip_error_set(error, ZIP_ER_MEMORY, 0);
+        return false;
+    }
+    buffer->fragment_offsets = offsets;
+    buffer->fragments_capacity = capacity;
+
+    return true;
 }
 
 
 static buffer_t *
-buffer_new_write(zip_uint64_t fragment_size)
-{
+buffer_new(const zip_buffer_fragment_t *fragments, zip_uint64_t nfragments, int free_data, zip_error_t *error) {
     buffer_t *buffer;
 
-    if ((buffer = buffer_new(fragment_size)) == NULL) {
-	return NULL;
+    if ((buffer = malloc(sizeof(*buffer))) == NULL) {
+        return NULL;
     }
 
-    if ((buffer->fragments = malloc(sizeof(*(buffer->fragments)))) == NULL) {
-	buffer_free(buffer);
-	return NULL;
-    }
-    buffer->fragments_capacity = 1;
+    buffer->offset = 0;
+    buffer->first_owned_fragment = 0;
+    buffer->size = 0;
+    buffer->fragments = NULL;
+    buffer->fragment_offsets = NULL;
     buffer->nfragments = 0;
-    buffer->free_data = 1;
+    buffer->fragments_capacity = 0;
+    buffer->shared_buffer = NULL;
+    buffer->shared_fragments = 0;
+
+    if (nfragments == 0) {
+        if ((buffer->fragment_offsets = malloc(sizeof(buffer->fragment_offsets[0]))) == NULL) {
+            free(buffer);
+            zip_error_set(error, ZIP_ER_MEMORY, 0);
+            return NULL;
+        }
+        buffer->fragment_offsets[0] = 0;
+    }
+    else {
+        zip_uint64_t i, j, offset;
+
+        if (!buffer_grow_fragments(buffer, nfragments, NULL)) {
+            zip_error_set(error, ZIP_ER_MEMORY, 0);
+            buffer_free(buffer);
+            return NULL;
+        }
+
+        offset = 0;
+        for (i = 0, j = 0; i < nfragments; i++) {
+            if (fragments[i].length == 0) {
+                continue;
+            }
+            if (fragments[i].data == NULL) {
+                zip_error_set(error, ZIP_ER_INVAL, 0);
+                buffer_free(buffer);
+                return NULL;
+            }
+            buffer->fragments[j].data = fragments[i].data;
+            buffer->fragments[j].length = fragments[i].length;
+            buffer->fragment_offsets[i] = offset;
+            /* TODO: overflow */
+            offset += fragments[i].length;
+            j++;
+        }
+        buffer->nfragments = j;
+        buffer->first_owned_fragment = free_data ? 0 : buffer->nfragments;
+        buffer->fragment_offsets[buffer->nfragments] = offset;
+        buffer->size = offset;
+    }
 
     return buffer;
 }
 
-
 static zip_int64_t
-buffer_read(buffer_t *buffer, zip_uint8_t *data, zip_uint64_t length)
-{
+buffer_read(buffer_t *buffer, zip_uint8_t *data, zip_uint64_t length) {
     zip_uint64_t n, i, fragment_offset;
 
     length = ZIP_MIN(length, buffer->size - buffer->offset);
 
     if (length == 0) {
-	return 0;
+        return 0;
     }
     if (length > ZIP_INT64_MAX) {
-	return -1;
+        return -1;
     }
 
-    i = buffer->offset / buffer->fragment_size;
-    fragment_offset = buffer->offset % buffer->fragment_size;
+    i = buffer->current_fragment;
+    fragment_offset = buffer->offset - buffer->fragment_offsets[i];
     n = 0;
     while (n < length) {
-	zip_uint64_t left = ZIP_MIN(length - n, buffer->fragment_size - fragment_offset);
-	
-	memcpy(data + n, buffer->fragments[i] + fragment_offset, left);
+        zip_uint64_t left = ZIP_MIN(length - n, buffer->fragments[i].length - fragment_offset);
+#if ZIP_UINT64_MAX > SIZE_MAX
+        left = ZIP_MIN(left, SIZE_MAX);
+#endif
+
+        (void)memcpy_s(data + n, (size_t)left, buffer->fragments[i].data + fragment_offset, (size_t)left);
 
-	n += left;
-	i++;
-	fragment_offset = 0;
+        if (left == buffer->fragments[i].length - fragment_offset) {
+            i++;
+        }
+        n += left;
+        fragment_offset = 0;
     }
 
     buffer->offset += n;
+    buffer->current_fragment = i;
     return (zip_int64_t)n;
 }
 
 
 static int
-buffer_seek(buffer_t *buffer, void *data, zip_uint64_t len, zip_error_t *error)
-{
+buffer_seek(buffer_t *buffer, void *data, zip_uint64_t len, zip_error_t *error) {
     zip_int64_t new_offset = zip_source_seek_compute_offset(buffer->offset, buffer->size, data, len, error);
-    
+
     if (new_offset < 0) {
         return -1;
     }
-    
+
     buffer->offset = (zip_uint64_t)new_offset;
+    buffer->current_fragment = buffer_find_fragment(buffer, buffer->offset);
     return 0;
 }
 
 
 static zip_int64_t
-buffer_write(buffer_t *buffer, const zip_uint8_t *data, zip_uint64_t length, zip_error_t *error)
-{
-    zip_uint64_t n, i, fragment_offset;
-    zip_uint8_t **fragments;
+buffer_write(buffer_t *buffer, const zip_uint8_t *data, zip_uint64_t length, zip_error_t *error) {
+    zip_uint64_t copied, i, fragment_offset, capacity;
 
-    if (buffer->offset + length + buffer->fragment_size - 1 < length) {
-	zip_error_set(error, ZIP_ER_INVAL, 0);
-	return -1;
+    if (buffer->offset + length + WRITE_FRAGMENT_SIZE - 1 < length) {
+        zip_error_set(error, ZIP_ER_INVAL, 0);
+        return -1;
     }
 
     /* grow buffer if needed */
-    if (buffer->offset + length > buffer->nfragments * buffer->fragment_size) {
-	zip_uint64_t needed_fragments = (buffer->offset + length + buffer->fragment_size - 1) / buffer->fragment_size;
-	
-	if (needed_fragments > buffer->fragments_capacity) {
-	    zip_uint64_t new_capacity = buffer->fragments_capacity;
-
-	    while (new_capacity < needed_fragments) {
-		new_capacity *= 2;
-	    }
-
-	    fragments = realloc(buffer->fragments, new_capacity * sizeof(*fragments));
-
-	    if (fragments == NULL) {
-		zip_error_set(error, ZIP_ER_MEMORY, 0);
-		return -1;
-	    }
-
-	    buffer->fragments = fragments;
-	    buffer->fragments_capacity = new_capacity;
-	}
-
-	while (buffer->nfragments < needed_fragments) {
-	    if ((buffer->fragments[buffer->nfragments] = malloc(buffer->fragment_size)) == NULL) {
-		zip_error_set(error, ZIP_ER_MEMORY, 0);
-		return -1;
-	    }
-	    buffer->nfragments++;
-	}
-    }
-
-    i = buffer->offset / buffer->fragment_size;
-    fragment_offset = buffer->offset % buffer->fragment_size;
-    n = 0;
-    while (n < length) {
-	zip_uint64_t left = ZIP_MIN(length - n, buffer->fragment_size - fragment_offset);
-		
-	memcpy(buffer->fragments[i] + fragment_offset, data + n, left);
+    capacity = buffer_capacity(buffer);
+    if (buffer->offset + length > capacity) {
+        zip_uint64_t needed_fragments = buffer->nfragments + (length - (capacity - buffer->offset) + WRITE_FRAGMENT_SIZE - 1) / WRITE_FRAGMENT_SIZE;
+
+        if (needed_fragments > buffer->fragments_capacity) {
+            zip_uint64_t new_capacity = buffer->fragments_capacity;
+
+            if (new_capacity == 0) {
+                new_capacity = 16;
+            }
+            while (new_capacity < needed_fragments) {
+                new_capacity *= 2;
+            }
+
+            if (!buffer_grow_fragments(buffer, new_capacity, error)) {
+                zip_error_set(error, ZIP_ER_MEMORY, 0);
+                return -1;
+            }
+        }
+
+        while (buffer->nfragments < needed_fragments) {
+            if ((buffer->fragments[buffer->nfragments].data = malloc(WRITE_FRAGMENT_SIZE)) == NULL) {
+                zip_error_set(error, ZIP_ER_MEMORY, 0);
+                return -1;
+            }
+            buffer->fragments[buffer->nfragments].length = WRITE_FRAGMENT_SIZE;
+            buffer->nfragments++;
+            capacity += WRITE_FRAGMENT_SIZE;
+            buffer->fragment_offsets[buffer->nfragments] = capacity;
+        }
+    }
+
+    i = buffer->current_fragment;
+    fragment_offset = buffer->offset - buffer->fragment_offsets[i];
+    copied = 0;
+    while (copied < length) {
+        zip_uint64_t n = ZIP_MIN(ZIP_MIN(length - copied, buffer->fragments[i].length - fragment_offset), SIZE_MAX);
+#if ZIP_UINT64_MAX > SIZE_MAX
+        n = ZIP_MIN(n, SIZE_MAX);
+#endif
+
+        (void)memcpy_s(buffer->fragments[i].data + fragment_offset, (size_t)n, data + copied, (size_t)n);
 
-	n += left;
-	i++;
-	fragment_offset = 0;
+        if (n == buffer->fragments[i].length - fragment_offset) {
+            i++;
+            fragment_offset = 0;
+        }
+        else {
+            fragment_offset += n;
+        }
+        copied += n;
     }
 
-    buffer->offset += n;
+    buffer->offset += copied;
+    buffer->current_fragment = i;
     if (buffer->offset > buffer->size) {
-	buffer->size = buffer->offset;
+        buffer->size = buffer->offset;
     }
 
-    return (zip_int64_t)n;
+    return (zip_int64_t)copied;
 }