Add zipAlreadyThere() to minizip zip.c to help avoid duplicates.

3 files changed, 612 insertions, 10 deletions

diff --git a/contrib/minizip/skipset.h b/contrib/minizip/skipset.h
new file mode 100644
index 0000000..f829b18
--- /dev/null
+++ b/contrib/minizip/skipset.h
@@ -0,0 +1,359 @@
+// skipset.h -- set operations using a skiplist
+// Copyright (C) 2024 Mark Adler
+// See MiniZip_info.txt for the license.
+
+// This implements a skiplist set, i.e. just keys, no data, with ~O(log n) time
+// insert and search operations. The application defines the type of a key, and
+// provides a function to compare two keys.
+
+// This header is not definitions of functions found in another source file --
+// it creates the set functions, with the application's key type, right where
+// the #include is. Before this header is #included, these must be defined:
+//
+// 1. A macro or typedef for set_key_t, the type of a key.
+// 2. A macro or function set_cmp(a, b) to compare two keys. The return values
+//    are < 0 for a < b, 0 for a == b, and > 0 for a > b.
+// 3. A macro or function set_drop(s, k) to release the key k's resources, if
+//    any, when doing a set_end() or set_clear(). s is a pointer to the set
+//    that key is in, for use with set_free() if desired.
+//
+// Example usage:
+//
+//      typedef int set_key_t;
+//      #define set_cmp(a, b) ((a) < (b) ? -1 : (a) == (b) ? 0 : 1)
+//      #define set_drop(s, k)
+//      #include "skipset.h"
+//
+//      int test(void) {        // return 0: good, 1: bad, -1: out of memory
+//          set_t set;
+//          if (setjmp(set.env))
+//              return -1;
+//          set_start(&set);
+//          set_insert(&set, 2);
+//          set_insert(&set, 1);
+//          set_insert(&set, 7);
+//          int bad = !set_found(&set, 2);
+//          bad = bad || set_found(&set, 5);
+//          set_end(&set);
+//          return bad;
+//      }
+//
+// Interface summary (see more details below):
+// - set_t is the type of the set being operated on (a set_t pointer is passed)
+// - set_start() initializes a new, empty set (initialize set.env first)
+// - set_insert() inserts a new key into the set, or not if it's already there
+// - set_found() determines whether or not a key is in the set
+// - set_end() ends the use of the set, freeing all memory
+// - set_clear() empties the set, equivalent to set_end() and then set_start()
+// - set_ok() checks if set appears to be usable, i.e. started and not ended
+//
+// Auxiliary functions available to the application:
+// - set_alloc() allocates memory with optional tracking (#define SET_TRACK)
+// - set_free() deallocates memory allocated by set_alloc()
+// - set_rand() returns 32 random bits (seeded by set_start())
+
+#ifndef SKIPSET_H
+#define SKIPSET_H
+
+#include <stdlib.h>     // realloc(), free(), NULL, size_t
+#include <setjmp.h>     // jmp_buf, longjmp()
+#include <errno.h>      // ENOMEM
+#include <stdint.h>     // int16_t, uint32_t, uint64_t
+#include <time.h>       // time(), clock()
+#include <assert.h>     // assert.h
+
+// Structures and functions below noted as "--private--" should not be used by
+// the application. set_t is partially private and partially public -- see the
+// comments there.
+
+// There is no POSIX random() in MSVC, and rand() is awful. For portability, we
+// cannot rely on a library function for random numbers. Instead we use the
+// fast and effective algorithm below, invented by Melissa O'Neill.
+
+// *Really* minimal PCG32 code / (c) 2014 M.E. O'Neill / www.pcg-random.org
+// Licensed under Apache License 2.0 (NO WARRANTY, etc. see website)
+// --private-- Random number generator state.
+typedef struct {
+    uint64_t state;     // 64-bit generator state
+    uint64_t inc;       // 63-bit sequence id
+} set_rand_t;
+// --private-- Initialize the state *gen using seed and seq. seed seeds the
+// advancing 64-bit state. seq is a sequence selection constant.
+void set_seed(set_rand_t *gen, uint64_t seed, uint64_t seq) {
+    gen->inc = (seq << 1) | 1;
+    gen->state = (seed + gen->inc) * 6364136223846793005ULL + gen->inc;
+}
+// Return 32 random bits, advancing the state *gen.
+uint32_t set_rand(set_rand_t *gen) {
+    uint64_t state = gen->state;
+    gen->state = state * 6364136223846793005ULL + gen->inc;
+    uint32_t mix = (uint32_t)(((state >> 18) ^ state) >> 27);
+    int rot = state >> 59;
+    return (mix >> rot) | (mix << ((-rot) & 31));
+}
+// End of PCG32 code.
+
+// --private-- Linked-list node.
+typedef struct set_node_s set_node_t;
+struct set_node_s {
+    set_key_t key;          // the key (not used for head or path)
+    int16_t size;           // number of allocated pointers in right[]
+    int16_t fill;           // number of pointers in right[] filled in
+    set_node_t **right;     // pointer for each level, each to the right
+};
+
+// A set. The application sets env, may use gen with set_rand(), and may read
+// allocs and memory. The remaining variables are --private-- .
+typedef struct set_s {
+    set_node_t *head;       // skiplist head -- no key, just links
+    set_node_t *path;       // right[] is path to key from set_found()
+    set_node_t *node;       // node under construction, in case of longjmp()
+    int16_t depth;          // maximum depth of the skiplist
+    uint64_t ran;           // a precious trove of random bits
+    set_rand_t gen;         // random number generator state
+    jmp_buf env;            // setjmp() environment for allocation errors
+#ifdef SET_TRACK
+    size_t allocs;          // number of allocations
+    size_t memory;          // total amount of allocated memory (>= requests)
+#endif
+} set_t;
+
+// Memory allocation and deallocation. set_alloc(set, ptr, size) returns a
+// pointer to an allocation of size bytes if ptr is NULL, or the previous
+// allocation ptr resized to size bytes. set_alloc() will never return NULL.
+// set_free(set, ptr) frees an allocation created by set_alloc(). These may be
+// used by the application. e.g. if allocation tracking is desired.
+#ifdef SET_TRACK
+// Track the number of allocations and the total backing memory size.
+#  if defined(_WIN32)
+#    include <malloc.h>
+#    define SET_ALLOC_SIZE(ptr) _msize(ptr)
+#  elif defined(__MACH__)
+#    include <malloc/malloc.h>
+#    define SET_ALLOC_SIZE(ptr) malloc_size(ptr)
+#  elif defined(__linux__)
+#    include <malloc.h>
+#    define SET_ALLOC_SIZE(ptr) malloc_usable_size(ptr)
+#  elif defined(__FreeBSD__)
+#    include <malloc_np.h>
+#    define SET_ALLOC_SIZE(ptr) malloc_usable_size(ptr)
+#  elif defined(__NetBSD__)
+#    include <jemalloc/jemalloc.h>
+#    define SET_ALLOC_SIZE(ptr) malloc_usable_size(ptr)
+#  else     // e.g. OpenBSD
+#    define SET_ALLOC_SIZE(ptr) 0
+#  endif
+// With tracking.
+void *set_alloc(set_t *set, void *ptr, size_t size) {
+    size_t had = ptr == NULL ? 0 : SET_ALLOC_SIZE(ptr);
+    void *mem = realloc(ptr, size);
+    if (mem == NULL)
+        longjmp(set->env, ENOMEM);
+    set->allocs += ptr == NULL;
+    set->memory += SET_ALLOC_SIZE(mem) - had;
+    return mem;
+}
+void set_free(set_t *set, void *ptr) {
+    if (ptr != NULL) {
+        set->allocs--;
+        set->memory -= SET_ALLOC_SIZE(ptr);
+        free(ptr);
+    }
+}
+#else
+// Without tracking.
+void *set_alloc(set_t *set, void *ptr, size_t size) {
+    void *mem = realloc(ptr, size);
+    if (mem == NULL)
+        longjmp(set->env, ENOMEM);
+    return mem;
+}
+void set_free(set_t *set, void *ptr) {
+    (void)set;
+    free(ptr);
+}
+#endif
+
+// --private-- Grow node's array right[] as needed to be able to hold at least
+// want links. If fill is true, assure that the first want links are filled in,
+// setting them to set->head if not previously filled in. Otherwise it is
+// assumed that the first want links are about to be filled in.
+void set_grow(set_t *set, set_node_t *node, int want, int fill) {
+    if (node->size < want) {
+        int more = node->size ? node->size : 1;
+        while (more < want)
+            more <<= 1;
+        node->right = set_alloc(set, node->right, more * sizeof(set_node_t *));
+        node->size = (int16_t)more;
+    }
+    int i;
+    if (fill)
+        for (i = node->fill; i < want; i++)
+            node->right[i] = set->head;
+    node->fill = (int16_t)want;
+}
+
+// --private-- Return a new node. key is left uninitialized.
+set_node_t *set_node(set_t *set) {
+    set_node_t *node = set_alloc(set, NULL, sizeof(set_node_t));
+    node->size = 0;
+    node->fill = 0;
+    node->right = NULL;
+    return node;
+}
+
+// --private-- Free the list linked from head, along with the keys.
+void set_sweep(set_t *set) {
+    set_node_t *step = set->head->right[0];
+    while (step != set->head) {
+        set_node_t *next = step->right[0];      // save link to next node
+        set_drop(set, step->key);
+        set_free(set, step->right);
+        set_free(set, step);
+        step = next;
+    }
+}
+
+// Initialize a new set. set->env must be initialized using setjmp() before
+// set_start() is called. A longjmp(set->env, ENOMEM) will be used to handle a
+// memory allocation failure during any of the operations. (See setjmp.h and
+// errno.h.) The set can still be used if this happens, assuming that it didn't
+// happen during set_start(). Whether set_start() completed or not, set_end()
+// can be used to free the set's memory after a longjmp().
+void set_start(set_t *set) {
+#ifdef SET_TRACK
+    set->allocs = 0;
+    set->memory = 0;
+#endif
+    set->head = set->path = set->node = NULL;   // in case set_node() fails
+    set->path = set_node(set);
+    set->head = set_node(set);
+    set_grow(set, set->head, 1, 1); // one link back to head for an empty set
+    *(unsigned char *)&set->head->key = 137;    // set id
+    set->depth = 0;
+    set_seed(&set->gen, (uint64_t)time(NULL) * (uint64_t)clock(), 0);
+    set->ran = 1;
+}
+
+// Return true if *set appears to be in a usable state. If *set has been zeroed
+// out, then set_ok(set) will be false and set_end(set) will be safe.
+int set_ok(set_t *set) {
+    return set->head != NULL &&
+           set->head->right != NULL &&
+           *(unsigned char *)&set->head->key == 137;
+}
+
+// Empty the set. This frees the memory used for the previous set contents.
+// After set_clear(), *set is ready for use, as if after a set_start().
+void set_clear(set_t *set) {
+    assert(set_ok(set) && "improper use");
+
+    // Free all the keys and their nodes.
+    set_sweep(set);
+
+    // Leave the head and path allocations as is. Clear their contents, with
+    // head pointing to itself and setting depth to zero, for an empty set.
+    set->head->right[0] = set->head;
+    set->head->fill = 1;
+    set->path->fill = 0;
+    set->depth = 0;
+}
+
+// Done using the set -- free all allocations. The only operation on *set
+// permitted after this is set_start(). Though another set_end() would do no
+// harm. This can be done at any time after a set_start(), or after a longjmp()
+// on any allocation failure, including during a set_start().
+void set_end(set_t *set) {
+    if (set->head != NULL) {
+        // Empty the set and free the head node.
+        if (set->head->right != NULL) {
+            set_sweep(set);
+            set_free(set, set->head->right);
+        }
+        set_free(set, set->head);
+        set->head = NULL;
+    }
+    if (set->path != NULL) {
+        // Free the path work area.
+        set_free(set, set->path->right);
+        set_free(set, set->path);
+        set->path = NULL;
+    }
+    if (set->node != NULL) {
+        // Free the node that was under construction when longjmp() hit.
+        set_drop(set, set->node->key);
+        set_free(set, set->node->right);
+        set_free(set, set->node);
+        set->node = NULL;
+    }
+}
+
+// Look for key. Return 1 if found or 0 if not. This also puts the path to get
+// there in set->path, for use by set_insert().
+int set_found(set_t *set, set_key_t key) {
+    assert(set_ok(set) && "improper use");
+
+    // Start at depth and work down and right as determined by key comparisons.
+    set_node_t *head = set->head, *here = head;
+    int i = set->depth;
+    set_grow(set, set->path, i + 1, 0);
+    do {
+        while (here->right[i] != head &&
+               set_cmp(here->right[i]->key, key) < 0)
+            here = here->right[i];
+        set->path->right[i] = here;
+    } while (i--);
+
+    // See if the key matches.
+    here = here->right[0];
+    return here != head && set_cmp(here->key, key) == 0;
+}
+
+// Insert the key key. Return 0 on success, or 1 if key is already in the set.
+int set_insert(set_t *set, set_key_t key) {
+    assert(set_ok(set) && "improper use");
+
+    if (set_found(set, key))
+        // That key is already in the set.
+        return 1;
+
+    // Randomly generate a new level-- level 0 with probability 1/2, 1 with
+    // probability 1/4, 2 with probability 1/8, etc.
+    int level = 0;
+    for (;;) {
+        if (set->ran == 1)
+            // Ran out. Get another 32 random bits.
+            set->ran = set_rand(&set->gen) | (1ULL << 32);
+        int bit = set->ran & 1;
+        set->ran >>= 1;
+        if (bit)
+            break;
+        assert(level < 32767 &&
+               "Overhead, without any fuss, the stars were going out.");
+        level++;
+    }
+    if (level > set->depth) {
+        // The maximum depth is now deeper. Update the structures.
+        set_grow(set, set->path, level + 1, 1);
+        set_grow(set, set->head, level + 1, 1);
+        set->depth = (int16_t)level;
+    }
+
+    // Make a new node for the provided key, and insert it in the lists up to
+    // and including level.
+    set->node = set_node(set);
+    set->node->key = key;
+    set_grow(set, set->node, level + 1, 0);
+    int i;
+    for (i = 0; i <= level; i++) {
+        set->node->right[i] = set->path->right[i]->right[i];
+        set->path->right[i]->right[i] = set->node;
+    }
+    set->node = NULL;
+    return 0;
+}
+
+#else
+#error ** another skiplist set already created here
+// Would need to implement a prefix in order to support multiple sets.
+#endif
diff --git a/contrib/minizip/zip.c b/contrib/minizip/zip.c
index a6329ae..d16e9ae 100644
--- a/contrib/minizip/zip.c
+++ b/contrib/minizip/zip.c
@@ -123,6 +123,19 @@ typedef struct linkedlist_data_s
 } linkedlist_data;
 
 
+// zipAlreadyThere() set functions for a set of zero-terminated strings, and
+// a block_t type for reading the central directory datablocks.
+typedef char const *set_key_t;
+#define set_cmp(a, b) strcmp(a, b)
+#define set_drop(s, k) set_free(s, (void *)(intptr_t)(k))
+#include "skipset.h"
+typedef struct {
+    unsigned char *next;        // next byte in datablock data
+    size_t left;                // number of bytes left in data (at least)
+    linkedlist_datablock_internal *node;    // current datablock
+} block_t;
+
+
 typedef struct
 {
     z_stream stream;            /* zLib stream structure for inflate */
@@ -174,6 +187,10 @@ typedef struct
     char *globalcomment;
 #endif
 
+    // Support for zipAlreadyThere().
+    set_t set;              // set for detecting name collisions
+    block_t block;          // block for reading the central directory
+
 } zip64_internal;
 
 
@@ -264,6 +281,223 @@ local int add_data_in_datablock(linkedlist_data* ll, const void* buf, uLong len)
     return ZIP_OK;
 }
 
+// zipAlreadyThere() operations. "set" in the zip internal structure keeps the
+// set of names that are in the under-construction central directory so far. A
+// skipset provides ~O(log n) time insertion and searching. Central directory
+// records, stored in a linked list of allocated memory datablocks, is read
+// through "block" in the zip internal structure.
+
+// The block_*() functions support extracting the central directory file names
+// from the datablocks. They are designed to support a growing directory by
+// automatically continuing once more data has been appended to the linked
+// datablocks.
+
+// Initialize *block to the head of list. This should only be called once the
+// list has at least some data in it, i.e. list->first_block is not NULL.
+local void block_init(block_t *block, linkedlist_data *list) {
+    block->node = list->first_block;
+    block->next = block->node->data;
+    block->left = block->node->filled_in_this_block;
+}
+
+// Mark *block as bad, with all subsequent reads returning end, even if more
+// data is added to the datablocks. This is invoked if the central directory is
+// invalid, so there is no longer any point in attempting to interpret it.
+local void block_stop(block_t *block) {
+    block->left = 0;
+    block->next = NULL;
+}
+
+// Return true if *block has reached the end of the data in the datablocks.
+local int block_end(block_t *block) {
+    linkedlist_datablock_internal *node = block->node;
+    if (node == NULL)
+        // This block was previously terminated with extreme prejudice.
+        return 1;
+    if (block->next < node->data + node->filled_in_this_block)
+        // There are more bytes to read in the current datablock.
+        return 0;
+    while (node->next_datablock != NULL) {
+        if (node->filled_in_this_block != 0)
+            // There are some bytes in a later datablock.
+            return 0;
+        node = node->next_datablock;
+    }
+    // Reached the end of the list of datablocks. There's nothing.
+    return 1;
+}
+
+// Return one byte from *block, or -1 if the end is reached.
+local int block_get(block_t *block) {
+    while (block->left == 0) {
+        if (block->node == NULL)
+            // We've been marked bad. Return end.
+            return -1;
+        // Update left in case more was filled in since we were last here.
+        block->left = block->node->filled_in_this_block -
+                      (block->next - block->node->data);
+        if (block->left != 0)
+            // There was indeed more data appended in the current datablock.
+            break;
+        if (block->node->next_datablock == NULL)
+            // No more data here, and there is no next datablock. At the end.
+            return -1;
+        // Try the next datablock for more data.
+        block->node = block->node->next_datablock;
+        block->next = block->node->data;
+        block->left = block->node->filled_in_this_block;
+    }
+    // We have a byte to return.
+    block->left--;
+    return *block->next++;
+}
+
+// Return a 16-bit unsigned little-endian value from block, or a negative value
+// if the end is reached.
+local long block_get2(block_t *block) {
+    long got = block_get(block);
+    return got | ((long)block_get(block) << 8);
+}
+
+// Read up to len bytes from block into buf. Return the number of bytes read.
+local size_t block_read(block_t *block, unsigned char *buf, size_t len) {
+    size_t need = len;
+    while (need) {
+        if (block->left == 0) {
+            // Get a byte to update and step through the linked list as needed.
+            int got = block_get(block);
+            if (got == -1)
+                // Reached the end.
+                break;
+            *buf++ = (unsigned char)got;
+            need--;
+            continue;
+        }
+        size_t take = need > block->left ? block->left : need;
+        memcpy(buf, block->next, take);
+        block->next += take;
+        block->left -= take;
+        buf += take;
+        need -= take;
+    }
+    return len - need;      // return the number of bytes copied
+}
+
+// Skip n bytes in block. Return 0 on success or -1 if there are less than n
+// bytes to the end.
+local int block_skip(block_t *block, size_t n) {
+    while (n > block->left) {
+        n -= block->left;
+        block->next += block->left;
+        block->left = 0;
+        if (block_get(block) == -1)
+            return -1;
+        n--;
+    }
+    block->next += n;
+    block->left -= n;
+    return 0;
+}
+
+// Process the next central directory record at *block. Return the allocated,
+// zero-terminated file name, or NULL for end of input or invalid data. If
+// invalid, *block is marked bad. This uses *set for the allocation of memory.
+local char *block_central_name(block_t *block, set_t *set) {
+    char *name = NULL;
+    for (;;) {
+        if (block_end(block))
+            // At the end of the central directory (so far).
+            return NULL;
+
+        // Check for a central directory record signature.
+        if (block_get2(block) != (CENTRALHEADERMAGIC & 0xffff) ||
+            block_get2(block) != (CENTRALHEADERMAGIC >> 16))
+            // Incorrect signature.
+            break;
+
+        // Go through the remaining fixed-length portion of the record,
+        // extracting the lengths of the three variable-length fields.
+        block_skip(block, 24);
+        unsigned flen = block_get2(block);      // file name length
+        unsigned xlen = block_get2(block);      // extra field length
+        unsigned clen = block_get2(block);      // comment field length
+        if (block_skip(block, 12) == -1)
+            // Premature end of the record.
+            break;
+
+        // Extract the name and skip over the extra and comment fields.
+        name = set_alloc(set, NULL, flen + 1);
+        if (block_read(block, (unsigned char *)name, flen) < flen ||
+            block_skip(block, xlen + clen) == -1)
+            // Premature end of the record.
+            break;
+
+        // Check for embedded nuls in the name.
+        if (memchr(name, 0, flen) != NULL) {
+            // This name can never match the zero-terminated name provided to
+            // zipAlreadyThere(), so we discard it and go back to get another
+            // name. (Who the heck is putting nuls inside their zip file entry
+            // names anyway?)
+            set_free(set, name);
+            continue;
+        }
+
+        // All good. Return the zero-terminated file name.
+        name[flen] = 0;
+        return name;
+    }
+
+    // Invalid signature or premature end of the central directory record.
+    // Abandon trying to process the central directory.
+    set_free(set, name);
+    block_stop(block);
+    return NULL;
+}
+
+// Return 0 if name is not in the central directory so far, 1 if it is, -1 if
+// the central directory is invalid, -2 if out of memory, or ZIP_PARAMERROR if
+// file is NULL.
+extern int ZEXPORT zipAlreadyThere(zipFile file, char const *name) {
+    zip64_internal *zip = file;
+    if (zip == NULL)
+        return ZIP_PARAMERROR;
+    if (zip->central_dir.first_block == NULL)
+        // No central directory yet, so no, name isn't there.
+        return 0;
+    if (setjmp(zip->set.env)) {
+        // Memory allocation failure.
+        set_end(&zip->set);
+        return -2;
+    }
+    if (!set_ok(&zip->set)) {
+        // This is the first time here with some central directory content. We
+        // construct this set of names only on demand. Prepare set and block.
+        set_start(&zip->set);
+        block_init(&zip->block, &zip->central_dir);
+    }
+
+    // Update the set of names from the current central directory contents.
+    // This reads any new central directory records since the last time we were
+    // here.
+    for (;;) {
+        char *there = block_central_name(&zip->block, &zip->set);
+        if (there == NULL) {
+            if (zip->block.next == NULL)
+                // The central directory is invalid.
+                return -1;
+            break;
+        }
+
+        // Add there to the set.
+        if (set_insert(&zip->set, there))
+            // There's already a duplicate in the central directory! We'll just
+            // let this be and carry on.
+            set_free(&zip->set, there);
+    }
+
+    // Return true if name is in the central directory.
+    return set_found(&zip->set, name);
+}
 
 
 /****************************************************************************/
@@ -551,7 +785,7 @@ local ZPOS64_T zip64local_SearchCentralDir64(const zlib_filefunc64_32_def* pzlib
 
     for (i=(int)uReadSize-3; (i--)>0;)
     {
-      // Signature "0x07064b50" Zip64 end of central directory locater
+      // Signature "0x07064b50" Zip64 end of central directory locator
       if (((*(buf+i))==0x50) && ((*(buf+i+1))==0x4b) && ((*(buf+i+2))==0x06) && ((*(buf+i+3))==0x07))
       {
         uPosFound = uReadPos+(unsigned)i;
@@ -843,6 +1077,7 @@ extern zipFile ZEXPORT zipOpen3(const void *pathname, int append, zipcharpc* glo
     ziinit.number_entry = 0;
     ziinit.add_position_when_writing_offset = 0;
     init_linkedlist(&(ziinit.central_dir));
+    memset(&ziinit.set, 0, sizeof(set_t));  // make sure set appears dormant
 
 
 
@@ -1870,6 +2105,8 @@ extern int ZEXPORT zipClose(zipFile file, const char* global_comment) {
     }
     free_linkedlist(&(zi->central_dir));
 
+    set_end(&zi->set);          // set was zeroed, so this is safe
+
     pos = centraldir_pos_inzip - zi->add_position_when_writing_offset;
     if(pos >= 0xffffffff || zi->number_entry >= 0xFFFF)
     {
diff --git a/contrib/minizip/zip.h b/contrib/minizip/zip.h
index 3e230d3..1f7f0b2 100644
--- a/contrib/minizip/zip.h
+++ b/contrib/minizip/zip.h
@@ -35,7 +35,7 @@
 
         See header of zip.h
 
-*/
+ */
 
 #ifndef _zip12_H
 #define _zip12_H
@@ -127,12 +127,12 @@ extern zipFile ZEXPORT zipOpen64(const void *pathname, int append);
      If the zipfile cannot be opened, the return value is NULL.
      Else, the return value is a zipFile Handle, usable with other function
        of this zip package.
-*/
+ */
 
 /* Note : there is no delete function into a zipfile.
    If you want delete file into a zipfile, you must open a zipfile, and create another
    Of course, you can use RAW reading and writing to copy the file you did not want delete
-*/
+ */
 
 extern zipFile ZEXPORT zipOpen2(const char *pathname,
                                 int append,
@@ -186,7 +186,7 @@ extern int ZEXPORT zipOpenNewFileInZip64(zipFile file,
   zip64 is set to 1 if a zip64 extended information block should be added to the local file header.
                     this MUST be '1' if the uncompressed size is >= 0xffffffff.
 
-*/
+ */
 
 
 extern int ZEXPORT zipOpenNewFileInZip2(zipFile file,
@@ -311,12 +311,12 @@ extern int ZEXPORT zipWriteInFileInZip(zipFile file,
                                        unsigned len);
 /*
   Write data in the zipfile
-*/
+ */
 
 extern int ZEXPORT zipCloseFileInZip(zipFile file);
 /*
   Close the current file in the zipfile
-*/
+ */
 
 extern int ZEXPORT zipCloseFileInZipRaw(zipFile file,
                                         uLong uncompressed_size,
@@ -326,17 +326,23 @@ extern int ZEXPORT zipCloseFileInZipRaw64(zipFile file,
                                           ZPOS64_T uncompressed_size,
                                           uLong crc32);
 
+extern int ZEXPORT zipAlreadyThere(zipFile file,
+                                   char const* name);
+/*
+  See if name is already in file's central directory.
+ */
+
 /*
   Close the current file in the zipfile, for file opened with
     parameter raw=1 in zipOpenNewFileInZip2
   uncompressed_size and crc32 are value for the uncompressed size
-*/
+ */
 
 extern int ZEXPORT zipClose(zipFile file,
                             const char* global_comment);
 /*
   Close the zipfile
-*/
+ */
 
 
 extern int ZEXPORT zipRemoveExtraInfoBlock(char* pData, int* dataLen, short sHeader);
@@ -355,7 +361,7 @@ extern int ZEXPORT zipRemoveExtraInfoBlock(char* pData, int* dataLen, short sHea
 
                         Remove ZIP64 Extra information from a Local File Header extra field data
         zipRemoveExtraInfoBlock(pLocalHeaderExtraFieldData, &nLocalHeaderExtraFieldDataLen, 0x0001);
-*/
+ */
 
 #ifdef __cplusplus
 }