From 3bfb86f5418dff5e037cdc374eaa322851131f33 Mon Sep 17 00:00:00 2001
From: "Raphael S. Carvalho" <raphaelsc@cloudius-systems.com>
Date: Mon, 15 Jun 2015 10:19:21 -0300
Subject: [PATCH] sstables: add compress_max_size to compression

used to return maximum size which compressor may output.

Signed-off-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>
Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
---
 sstables/compress.cc | 17 +++++++++++++++++
 sstables/compress.hh | 12 +++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/sstables/compress.cc b/sstables/compress.cc
index 9df3d077c0..8fbcb2ee9a 100644
--- a/sstables/compress.cc
+++ b/sstables/compress.cc
@@ -36,12 +36,15 @@ void compression::update(uint64_t compressed_file_length) {
 void compression::set_compressor(compressor c) {
      if (c == compressor::lz4) {
          _compress = compress_lz4;
+         _compress_max_size = compress_max_size_lz4;
          name.value = "LZ4Compressor";
      } else if (c == compressor::snappy) {
          _compress = compress_snappy;
+         _compress_max_size = compress_max_size_snappy;
          name.value = "SnappyCompressor";
      } else if (c == compressor::deflate) {
          _compress = compress_deflate;
+         _compress_max_size = compress_max_size_deflate;
          name.value = "DeflateCompressor";
      } else {
          throw std::runtime_error("unsupported compressor type");
@@ -152,6 +155,20 @@ size_t compress_snappy(const char* input, size_t input_len,
     fail(unimplemented::cause::COMPRESSION);
 }
 
+size_t compress_max_size_lz4(size_t input_len) {
+    return LZ4_COMPRESSBOUND(input_len) + 4;
+}
+
+size_t compress_max_size_deflate(size_t input_len) {
+    // FIXME: implement.
+    fail(unimplemented::cause::COMPRESSION);
+}
+
+size_t compress_max_size_snappy(size_t input_len) {
+    // FIXME: implement.
+    fail(unimplemented::cause::COMPRESSION);
+}
+
 class compressed_file_data_source_impl : public data_source_impl {
     lw_shared_ptr<file> _file;
     sstables::compression* _compression_metadata;
diff --git a/sstables/compress.hh b/sstables/compress.hh
index bc7598ed7e..bcdfed9ccc 100644
--- a/sstables/compress.hh
+++ b/sstables/compress.hh
@@ -59,6 +59,12 @@ compress_func compress_lz4;
 compress_func compress_snappy;
 compress_func compress_deflate;
 
+typedef size_t compress_max_size_func(size_t input_len);
+
+compress_max_size_func compress_max_size_lz4;
+compress_max_size_func compress_max_size_snappy;
+compress_max_size_func compress_max_size_deflate;
+
 inline uint32_t init_checksum_adler32() {
     return adler32(0, Z_NULL, 0);
 }
@@ -95,6 +101,8 @@ private:
     // Variables determined from the above deserialized values, held for convenience:
     uncompress_func *_uncompress = nullptr;
     compress_func *_compress = nullptr;
+    // Return maximum length of data that compressor may output.
+    compress_max_size_func *_compress_max_size = nullptr;
     // Variables *not* found in the "Compression Info" file (added by update()):
     uint64_t _compressed_file_length;
 public:
@@ -140,7 +148,9 @@ public:
         }
         return _compress(input, input_len, output, output_len);
     }
-
+    size_t compress_max_size(size_t input_len) const {
+        return _compress_max_size(input_len);
+    }
     friend class sstable;
 };