From f0d7f6288162f33b8d86af64c5f451bf5a4e9f48 Mon Sep 17 00:00:00 2001
From: "Taro L. Saito" <leo@xerial.org>
Date: Thu, 23 Oct 2014 12:42:12 +0900
Subject: [PATCH] #89: Add SnappyIOException to distinguish empty input,
 incompatible format version, etc.

---
 .../org/xerial/snappy/SnappyErrorCode.java    |  6 ++++-
 .../org/xerial/snappy/SnappyIOException.java  | 23 ++++++++++++++++
 .../org/xerial/snappy/SnappyInputStream.java  | 27 +++++++++----------
 .../xerial/snappy/SnappyInputStreamTest.java  |  6 ++---
 4 files changed, 44 insertions(+), 18 deletions(-)
 create mode 100644 src/main/java/org/xerial/snappy/SnappyIOException.java

diff --git a/src/main/java/org/xerial/snappy/SnappyErrorCode.java b/src/main/java/org/xerial/snappy/SnappyErrorCode.java
index e3e520a..f1d8b6b 100755
--- a/src/main/java/org/xerial/snappy/SnappyErrorCode.java
+++ b/src/main/java/org/xerial/snappy/SnappyErrorCode.java
@@ -38,7 +38,11 @@ public enum SnappyErrorCode {
     PARSING_ERROR(2),
     NOT_A_DIRECT_BUFFER(3),
     OUT_OF_MEMORY(4),
-    FAILED_TO_UNCOMPRESS(5);
+    FAILED_TO_UNCOMPRESS(5),
+    EMPTY_INPUT(6),
+    INCOMPATIBLE_VERSION(7),
+    INVALID_CHUNK_SIZE(8)
+    ;
 
     public final int id;
 
diff --git a/src/main/java/org/xerial/snappy/SnappyIOException.java b/src/main/java/org/xerial/snappy/SnappyIOException.java
new file mode 100644
index 0000000..ee4c60c
--- /dev/null
+++ b/src/main/java/org/xerial/snappy/SnappyIOException.java
@@ -0,0 +1,23 @@
+package org.xerial.snappy;
+
+import java.io.IOException;
+
+/**
+ * Enhanced IOException with SnappyErrorCode
+ */
+public class SnappyIOException extends IOException {
+    private final SnappyErrorCode errorCode;
+
+    public SnappyIOException(SnappyErrorCode errorCode, String message) {
+        super(message);
+        this.errorCode = errorCode;
+    }
+
+    @Override
+    public String getMessage() {
+        return String.format("[%s] %s", errorCode.name(), super.getMessage());
+    }
+
+    public SnappyErrorCode getErrorCode() { return errorCode; }
+
+}
diff --git a/src/main/java/org/xerial/snappy/SnappyInputStream.java b/src/main/java/org/xerial/snappy/SnappyInputStream.java
index 0d39c67..a56dff1 100755
--- a/src/main/java/org/xerial/snappy/SnappyInputStream.java
+++ b/src/main/java/org/xerial/snappy/SnappyInputStream.java
@@ -83,6 +83,10 @@ public class SnappyInputStream extends InputStream
         }
 
         // Quick test of the header
+        if(readBytes == 0) {
+            // Snappy produces at least 1-byte result. So the empty input is not a valid input
+            throw new SnappyIOException(SnappyErrorCode.EMPTY_INPUT, "Cannot decompress empty stream");
+        }
         if (readBytes < header.length || header[0] != SnappyCodec.MAGIC_HEADER[0]) {
             // do the default uncompression
             readFully(header, readBytes);
@@ -93,8 +97,8 @@ public class SnappyInputStream extends InputStream
         if (codec.isValidMagicHeader()) {
             // The input data is compressed by SnappyOutputStream
             if (codec.version < SnappyCodec.MINIMUM_COMPATIBLE_VERSION) {
-                throw new IOException(String.format(
-                        "compressed with imcompatible codec version %d. At least version %d is required",
+                throw new SnappyIOException(SnappyErrorCode.INCOMPATIBLE_VERSION, String.format(
+                        "Compressed with an incompatible codec version %d. At least version %d is required",
                         codec.version, SnappyCodec.MINIMUM_COMPATIBLE_VERSION));
             }
         }
@@ -351,20 +355,15 @@ public class SnappyInputStream extends InputStream
         if (readBytes < chunkSize) {
             throw new IOException("failed to read chunk");
         }
-        try {
-            int uncompressedLength = Snappy.uncompressedLength(compressed, 0, chunkSize);
-            if (uncompressed == null || uncompressedLength > uncompressed.length) {
-                uncompressed = new byte[uncompressedLength];
-            }
-            int actualUncompressedLength = Snappy.uncompress(compressed, 0, chunkSize, uncompressed, 0);
-            if (uncompressedLength != actualUncompressedLength) {
-                throw new IOException("invalid uncompressed byte size");
-            }
-            uncompressedLimit = actualUncompressedLength;
+        int uncompressedLength = Snappy.uncompressedLength(compressed, 0, chunkSize);
+        if (uncompressed == null || uncompressedLength > uncompressed.length) {
+            uncompressed = new byte[uncompressedLength];
         }
-        catch (IOException e) {
-            throw new IOException("failed to uncompress the chunk: " + e.getMessage());
+        int actualUncompressedLength = Snappy.uncompress(compressed, 0, chunkSize, uncompressed, 0);
+        if (uncompressedLength != actualUncompressedLength) {
+            throw new SnappyIOException(SnappyErrorCode.INVALID_CHUNK_SIZE, String.format("expected %,d bytes, but decompressed chunk has %,d bytes", uncompressedLength, actualUncompressedLength));
         }
+        uncompressedLimit = actualUncompressedLength;
 
         return true;
     }
diff --git a/src/test/java/org/xerial/snappy/SnappyInputStreamTest.java b/src/test/java/org/xerial/snappy/SnappyInputStreamTest.java
index 011eb31..7e66c58 100755
--- a/src/test/java/org/xerial/snappy/SnappyInputStreamTest.java
+++ b/src/test/java/org/xerial/snappy/SnappyInputStreamTest.java
@@ -135,11 +135,11 @@ public class SnappyInputStreamTest
             SnappyInputStream in = new SnappyInputStream(new ByteArrayInputStream(new byte[0]));
             byte[] uncompressed = readFully(in);
             assertEquals(0, uncompressed.length);
-        }
-        catch(Exception e) {
             fail("should not reach here");
         }
-
+        catch(SnappyIOException e) {
+            assertEquals(SnappyErrorCode.EMPTY_INPUT, e.getErrorCode());
+        }
     }
 
 }