1 files changed, 57 insertions, 0 deletions
diff --git a/lib/libyaz0/yaz0.c b/lib/libyaz0/yaz0.c
new file mode 100644
index 0000000..20f94fb
--- /dev/null
+++ b/lib/libyaz0/yaz0.c
@@ -0,0 +1,57 @@
+#include "yaz0.h"
+#include "libmio0/utils.h"
+#include <stdlib.h>
+#include <string.h>
+
+uint8_t* yaz0_decode(const uint8_t* in, uint32_t* out_size) {
+    if (strncmp((const char*)in, "Yaz0", 4) != 0) {
+        return NULL;
+    }
+
+    uint32_t decompressed_size = read_u32_be(in + 4);
+    uint8_t* out = malloc(decompressed_size);
+    if (!out) {
+        return NULL;
+    }
+
+    uint32_t src = YAZ0_HEADER_LENGTH;
+    uint32_t dst = 0;
+    uint8_t group_head = 0;
+    int bits_left = 0;
+
+    while (dst < decompressed_size) {
+        if (bits_left == 0) {
+            group_head = in[src++];
+            bits_left = 8;
+        }
+
+        if (group_head & 0x80) {
+            /* literal byte */
+            out[dst++] = in[src++];
+        } else {
+            /* back-reference */
+            uint8_t b1 = in[src++];
+            uint8_t b2 = in[src++];
+
+            uint32_t dist = ((b1 & 0x0F) << 8) | b2;
+            uint32_t copy_src = dst - (dist + 1);
+            uint32_t count;
+
+            if (b1 >> 4) {
+                count = (b1 >> 4) + 2;
+            } else {
+                count = in[src++] + 0x12;
+            }
+
+            for (uint32_t i = 0; i < count; i++) {
+                out[dst++] = out[copy_src + i];
+            }
+        }
+
+        group_head <<= 1;
+        bits_left--;
+    }
+
+    *out_size = decompressed_size;
+    return out;
+}