updates to OSS-Fuzz integration

adapt more fuzz targets from zlib,
add zip fuzzer, zip dictionary.
update uncompress_fuzzer to seed the buffer length separately.

tests/compress_fuzzer.c

@@ -0,0 +1,88 @@
+/* Derived from zlib fuzzers at http://github.com/google/oss-fuzz/tree/master/projects/zlib,
+ * see ossfuzz.sh for full license text.
+*/
+
+#include <stdio.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <inttypes.h>
+#include "miniz.h"
+
+static const uint8_t *data;
+static size_t dataLen;
+
+static void check_compress_level(uint8_t *compr, size_t comprLen,
+                                 uint8_t *uncompr, size_t uncomprLen,
+                                 int level)
+{
+    compress2(compr, &comprLen, data, dataLen, level);
+    uncompress(uncompr, &uncomprLen, compr, comprLen);
+
+    /* Make sure compress + uncompress gives back the input data. */
+    assert(dataLen == uncomprLen);
+    assert(0 == memcmp(data, uncompr, dataLen));
+}
+
+#define put_byte(s, i, c) {s[i] = (unsigned char)(c);}
+
+static void write_zlib_header(uint8_t *s)
+{
+    unsigned level_flags = 0; /* compression level (0..3) */
+    unsigned w_bits = 8; /* window size log2(w_size)  (8..16) */
+    unsigned int header = (Z_DEFLATED + ((w_bits-8)<<4)) << 8;
+    header |= (level_flags << 6);
+
+    header += 31 - (header % 31);
+
+    /* s is guaranteed to be longer than 2 bytes. */
+    put_byte(s, 0, (unsigned char)(header >> 8));
+    put_byte(s, 1, (unsigned char)(header & 0xff));
+}
+
+static void check_decompress(uint8_t *compr, size_t comprLen)
+{
+    /* We need to write a valid zlib header of size two bytes. Copy the input data
+        in a larger buffer. Do not modify the input data to avoid libFuzzer error:
+        fuzz target overwrites its const input. */
+    size_t copyLen = dataLen + 2;
+    uint8_t *copy = malloc(copyLen);
+    memcpy(copy + 2, data, dataLen);
+    write_zlib_header(copy);
+
+    uncompress(compr, &comprLen, copy, copyLen);
+    free(copy);
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *d, size_t size)
+{
+    /* compressBound does not provide enough space for low compression levels. */
+    size_t comprLen = 100 + 2 * compressBound(size);
+    size_t uncomprLen = size;
+    uint8_t *compr, *uncompr;
+
+    /* Discard inputs larger than 1Mb. */
+    static size_t kMaxSize = 1024 * 1024;
+
+    if (size < 1 || size > kMaxSize)
+    return 0;
+
+    data = d;
+    dataLen = size;
+    compr = calloc(1, comprLen);
+    uncompr = calloc(1, uncomprLen);
+
+    check_compress_level(compr, comprLen, uncompr, uncomprLen, 1);
+    check_compress_level(compr, comprLen, uncompr, uncomprLen, 3);
+    check_compress_level(compr, comprLen, uncompr, uncomprLen, 6);
+    check_compress_level(compr, comprLen, uncompr, uncomprLen, 7);
+
+    check_decompress(compr, comprLen);
+
+    free(compr);
+    free(uncompr);
+
+    return 0;
+}