[openjk] 20/130: Add RLE compression

[Simon McVittie]

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smcv pushed a commit to branch debian/master
in repository openjk.

commit ae16dcf7c20dc13978b342d830527de1389fce99
Author: bibendovsky <bibendovsky at hotmail.com>
Date:   Mon Jul 4 20:58:58 2016 +0300

    Add RLE compression
---
 shared/qcommon/ojk_sg_archive.cpp   | 93 +++++++++++++++++++++++++++++++++++++
 shared/qcommon/ojk_sg_archive_fwd.h | 12 +++++
 2 files changed, 105 insertions(+)

diff --git a/shared/qcommon/ojk_sg_archive.cpp b/shared/qcommon/ojk_sg_archive.cpp
index 6e33274..0311e01 100644
--- a/shared/qcommon/ojk_sg_archive.cpp
+++ b/shared/qcommon/ojk_sg_archive.cpp
@@ -168,6 +168,99 @@ Archive& Archive::get_instance()
     return result;
 }
 
+int Archive::compress()
+{
+    auto src_size = static_cast<int>(io_buffer_.size());
+
+    rle_buffer_.resize(2 * src_size);
+
+    int src_count = 0;
+    int dst_index = 0;
+
+    while (src_count < src_size) {
+        auto src_index = src_count;
+        auto b = io_buffer_[src_index++];
+
+        while (src_index < src_size &&
+            (src_index - src_count) < 127 &&
+            io_buffer_[src_index] == b)
+        {
+            src_index += 1;
+        }
+
+        if ((src_index - src_count) == 1) {
+            while (src_index < src_size &&
+                (src_index - src_count) < 127 && (
+                    io_buffer_[src_index] != io_buffer_[src_index - 1] || (
+                        src_index > 1 &&
+                        io_buffer_[src_index] != io_buffer_[src_index - 2])))
+            {
+                src_index += 1;
+            }
+
+            while (src_index < src_size &&
+                io_buffer_[src_index] == io_buffer_[src_index - 1])
+            {
+                src_index -= 1;
+            }
+
+            rle_buffer_[dst_index++] =
+                static_cast<uint8_t>(src_count - src_index);
+
+            for (auto i = src_count; i < src_index; ++i) {
+                rle_buffer_[dst_index++] = io_buffer_[i];
+            }
+        } else {
+            rle_buffer_[dst_index++] =
+                static_cast<uint8_t>(src_index - src_count);
+
+            rle_buffer_[dst_index++] = b;
+        }
+
+        src_count = src_index;
+    }
+
+    rle_buffer_.resize(
+        dst_index);
+
+    return dst_index;
+}
+
+void Archive::decompress(
+    int dst_size)
+{
+    rle_buffer_.resize(
+        dst_size);
+
+    int src_index = 0;
+    int dst_index = 0;
+
+    while (dst_size > 0) {
+        auto count = static_cast<int8_t>(io_buffer_[src_index++]);
+
+        if (count > 0) {
+            std::uninitialized_fill_n(
+                &rle_buffer_[dst_index],
+                count,
+                io_buffer_[src_index++]);
+        } else {
+            if (count < 0) {
+                count = -count;
+
+                std::uninitialized_copy_n(
+                    &io_buffer_[src_index],
+                    count,
+                    &rle_buffer_[dst_index]);
+
+                src_index += count;
+            }
+        }
+
+        dst_index += count;
+        dst_size -= count;
+    }
+}
+
 std::string Archive::generate_path(
     const std::string& base_file_name)
 {
diff --git a/shared/qcommon/ojk_sg_archive_fwd.h b/shared/qcommon/ojk_sg_archive_fwd.h
index 574bb63..99ae628 100644
--- a/shared/qcommon/ojk_sg_archive_fwd.h
+++ b/shared/qcommon/ojk_sg_archive_fwd.h
@@ -149,6 +149,18 @@ private:
     // A current offset inside the I/O buffer.
     BufferOffset io_buffer_offset_;
 
+    // RLE codec buffer.
+    Buffer rle_buffer_;
+
+
+    // Compresses I/O buffer into RLE one.
+    // Returns a size of compressed data.
+    int compress();
+
+    // Decompresses I/O buffer into RLE one.
+    void decompress(
+        int dst_size);
+
 
     static std::string generate_path(
         const std::string& base_file_name);

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