patterns/zstd: Added ZSTD pattern (#68)

patterns/zstd.hexpat

@@ -0,0 +1,115 @@
+// https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md
+
+#pragma MIME application/zstd
+ 
+#include <std/io.pat>
+#include <std/mem.pat>
+#include <std/sys.pat>
+
+#define ZSTD_MAGIC_NUMBER 0xFD2FB528
+
+bitfield frame_header_descriptor_t {
+    frame_content_size_flag : 2;
+    single_segment_flag : 1;
+    unused_bit : 1;
+    reserved_bit : 1;
+    content_checksum_flag : 1;
+    dictionary_id_flag : 2;
+} [[left_to_right]];
+
+bitfield window_descriptor_t {
+    exponent : 5;
+    mantissa : 3;
+} [[left_to_right]];
+
+fn window_size(window_descriptor_t window_descriptor) {
+    u64 window_log = 10 + window_descriptor.exponent;
+    u64 window_base = 1 << window_log;
+    u64 window_add = (window_base / 8) * window_descriptor.mantissa;
+    u64 window_size = window_base + window_add;
+    return window_size;
+};
+
+struct frame_header_t {
+    frame_header_descriptor_t frame_header_descriptor;
+
+    if (!frame_header_descriptor.single_segment_flag){
+        window_descriptor_t window_descriptor;
+    }
+
+    if (frame_header_descriptor.dictionary_id_flag == 1) {
+        le u8 dictionary_id;
+    }
+    else if (frame_header_descriptor.dictionary_id_flag == 2) {
+        le u16 dictionary_id;
+    }
+    else if (frame_header_descriptor.dictionary_id_flag == 3) {
+        le u32 dictionary_id;
+    }
+
+    if (frame_header_descriptor.frame_content_size_flag == 0) { // 0
+        if (frame_header_descriptor.single_segment_flag) {
+            le u8 content_size;
+        }
+    }
+    else if (frame_header_descriptor.frame_content_size_flag == 1) {
+        le u16 content_size;
+    }
+    else if (frame_header_descriptor.frame_content_size_flag == 2) {
+        le u32 content_size;
+    }
+    else {
+        le u64 content_size;
+    }
+};
+
+bitfield block_header_t {
+    block_size : 21;
+    block_type : 2;
+    last_block : 1;
+} [[left_to_right]];
+
+enum block_type : u8 {
+    raw_block = 0,
+    rle_block = 1,
+    compressed_block = 2,
+    reserved = 3
+};
+
+struct data_block_t {
+    block_header_t block_header;
+
+    if (block_header.last_block) {
+        last_block_flag = true;
+    }
+
+    if (block_header.block_type == block_type::raw_block) {
+        le u8 block_content[block_header.block_size];
+    }
+    else if (block_header.block_type == block_type::rle_block) {
+        le u8 block_content[1];
+    }
+    else if (block_header.block_type == block_type::compressed_block) {
+        le u8 block_content[block_header.block_size];
+    }
+    else {
+        std::error("The data block seems to be corrupted!");
+    }
+};
+
+struct content_checksum_t {
+    le u32 xxh64_hash;
+};
+
+struct zstd_frame_t {
+    le u32 magic_number;
+    std::assert(magic_number == ZSTD_MAGIC_NUMBER, "Invalid magic number!");
+    frame_header_t frame_header;
+    data_block_t data_block[while(!last_block_flag)];
+    if (frame_header.frame_header_descriptor.content_checksum_flag) {
+        content_checksum_t content_checksum;
+    }
+};
+
+bool last_block_flag = false;
+zstd_frame_t zstd_frame @ 0x00;