From e6f627bbc61819f236ca806baf7ccbfccb082d90 Mon Sep 17 00:00:00 2001
From: bharatnc <bharatnc@gmail.com>
Date: Tue, 6 Jul 2021 16:56:33 -0700
Subject: [PATCH] LZ4 - decompress read initial implementation

---
 src/IO/Lz4InflatingReadBuffer.cpp | 70 ++++++++++++++++++++++++++++---
 src/IO/Lz4InflatingReadBuffer.h   | 18 ++++++++
 2 files changed, 83 insertions(+), 5 deletions(-)

diff --git a/src/IO/Lz4InflatingReadBuffer.cpp b/src/IO/Lz4InflatingReadBuffer.cpp
index 722b18dee1d..57deef46a3a 100644
--- a/src/IO/Lz4InflatingReadBuffer.cpp
+++ b/src/IO/Lz4InflatingReadBuffer.cpp
@@ -4,24 +4,84 @@ namespace DB
 {
 namespace ErrorCodes
 {
-extern const int LZ4_DECODER_FAILED;
+    extern const int LZ4_DECODER_FAILED;
 }
 
 Lz4InflatingReadBuffer::Lz4InflatingReadBuffer(std::unique_ptr<ReadBuffer> in_, size_t buf_size, char * existing_memory, size_t alignment)
     : BufferWithOwnMemory<ReadBuffer>(buf_size, existing_memory, alignment), in(std::move(in_))
 {
-    /// TODO: Implementation
+    ret = 1;
+
+
+    dctx_status = LZ4F_createDecompressionContext(&dctx, LZ4F_VERSION);
+    if (LZ4F_isError(dctx_status))
+    {
+        throw Exception(
+            ErrorCodes::LZ4_DECODER_FAILED,
+            "LZ4 failed create decompression context LZ4F_dctx. LZ4F version: {}. Error: {}",
+            LZ4F_VERSION,
+            LZ4F_getErrorName(dctx_status),
+            ErrorCodes::LZ4_DECODER_FAILED);
+    }
 }
 
 Lz4InflatingReadBuffer::~Lz4InflatingReadBuffer()
 {
-   /// TODO: Implementation
+    LZ4F_freeDecompressionContext(dctx);
 }
 
 bool Lz4InflatingReadBuffer::nextImpl()
 {
-    /// TODO: Implementation
+    if (eof)
+        return false;
+
+
+    if (!in_available)
+    {
+        in->nextIfAtEnd();
+        in_available = in->buffer().end() - in->position();
+        src = reinterpret_cast<void *>(in->position());
+    }
+
+
+    src_capacity = internal_buffer.size();
+    dst = reinterpret_cast<void *>(internal_buffer.begin());
+
+
+    LZ4F_frameInfo_t info;
+    size_t consumed_size = src_capacity;
+    {   size_t const frame_info_res = LZ4F_getFrameInfo(dctx, &info, &src, &consumed_size);
+        if (LZ4F_isError(frame_info_res)) {
+            throw Exception(
+                ErrorCodes::LZ4_DECODER_FAILED,
+                "LZ4 failed to fetch get info LZ4F_getFrameInfo. LZ4F version: {}. Error: {}",
+                LZ4F_VERSION,
+                LZ4F_getErrorName(frame_info_res),
+                ErrorCodes::LZ4_DECODER_FAILED);
+        }
+    }
+
+    ret = LZ4F_decompress(dctx, dst, &dst_capacity, &src, &src_capacity, /* LZ4F_decompressOptions_t */ nullptr);
+    if (LZ4F_isError(ret)) {
+        printf("Decompression error: %s\n", LZ4F_getErrorName(ret));
+        throw Exception(
+            ErrorCodes::LZ4_DECODER_FAILED,
+            "LZ4 failed to fetch get info LZ4F_getFrameInfo. LZ4F version: {}. Error: {}",
+            LZ4F_VERSION,
+            LZ4F_getErrorName(ret),
+            ErrorCodes::LZ4_DECODER_FAILED);
+    }
+
+    in->position() = in->buffer().end() - in_available;
+    working_buffer.resize(internal_buffer.size() - src_capacity);
+
+
+    if (in->eof())
+    {
+        eof = true;
+        return !working_buffer.empty();
+    }
+
     return true;
 }
-
 }
diff --git a/src/IO/Lz4InflatingReadBuffer.h b/src/IO/Lz4InflatingReadBuffer.h
index e87dcb740eb..1282e276717 100644
--- a/src/IO/Lz4InflatingReadBuffer.h
+++ b/src/IO/Lz4InflatingReadBuffer.h
@@ -5,6 +5,7 @@
 #include <IO/ReadBuffer.h>
 
 #include <lz4.h>
+#include <lz4frame.h>
 
 
 namespace DB
@@ -28,6 +29,23 @@ private:
     bool nextImpl() override;
 
     std::unique_ptr<ReadBuffer> in;
+
+    size_t ret;
+
+    void * src;
+    void * dst;
+
+    size_t src_capacity;
+    size_t dst_capacity;
+
+    size_t in_available;
+
+    LZ4F_dctx* dctx;
+    size_t dctx_status;
+
+
+    bool eof = false;
+
 };
 
 }