Add eof() function to reader APIs (#105)

Summary:
Pull Request resolved: #105

We need to know whether the underlying source has any more data, otherwise we won't know whether to stop reading

Reviewed By: elliottlawrence

Differential Revision: D34967134

fbshipit-source-id: 8ac2f71747e534a63f75cac8e30aaf599922cab6

Author: Aditya Shastri

fbpcf/io/api/CloudFileReader.cpp

@@ -20,6 +20,9 @@ int CloudFileReader::close() {
 size_t CloudFileReader::read(std::vector<char>& /* buf */) {
   return 0;
 }
+bool CloudFileReader::eof() {
+  return false;
+}
 
 CloudFileReader::~CloudFileReader() {
   close();

fbpcf/io/api/CloudFileReader.h

@@ -24,6 +24,7 @@ class CloudFileReader : public IReaderCloser {
 
   int close() override;
   size_t read(std::vector<char>& buf) override;
+  bool eof() override;
   ~CloudFileReader() override;
 };
 

fbpcf/io/api/FileReader.cpp

@@ -32,6 +32,10 @@ size_t FileReader::read(std::vector<char>& buf) {
   return childReader_->read(buf);
 }
 
+bool FileReader::eof() {
+  return childReader_->eof();
+}
+
 int FileReader::close() {
   return childReader_->close();
 }

fbpcf/io/api/FileReader.h

@@ -27,6 +27,7 @@ class FileReader : public IReaderCloser {
 
   int close() override;
   size_t read(std::vector<char>& buf) override;
+  bool eof() override;
   ~FileReader() override;
 
  private:

fbpcf/io/api/IReader.h

@@ -25,6 +25,11 @@ class IReader {
    * read
    */
   virtual size_t read(std::vector<char>& buf) = 0;
+  /*
+   * eof() returns whether there is any more
+   * data left in the file
+   */
+  virtual bool eof() = 0;
   virtual ~IReader() = default;
 };
 

fbpcf/io/api/LocalFileReader.cpp

@@ -37,6 +37,10 @@ size_t LocalFileReader::read(std::vector<char>& buf) {
   return inputStream_->gcount();
 }
 
+bool LocalFileReader::eof() {
+  return inputStream_->eof();
+}
+
 LocalFileReader::~LocalFileReader() {
   close();
 }

fbpcf/io/api/LocalFileReader.h

@@ -27,6 +27,7 @@ class LocalFileReader : public IReaderCloser {
 
   int close() override;
   size_t read(std::vector<char>& buf) override;
+  bool eof() override;
   ~LocalFileReader() override;
 
  private:

fbpcf/io/api/SocketReader.h

@@ -34,6 +34,7 @@ class SocketReader : public IReaderCloser {
 
   int close() override;
   size_t read(std::vector<char>& buf) override;
+  bool eof() override;
   ~SocketReader() override;
 };
 

fbpcf/io/api/test/LocalFileReaderTest.cpp

@@ -18,6 +18,8 @@ TEST(LocalFileReaderTest, testReadingFromFile) {
       IOTestHelper::getBaseDirFromPath(__FILE__) +
       "data/local_file_reader_test_file.txt");
 
+  EXPECT_FALSE(reader->eof());
+
   /*
     CASE 1A
     Buffer of size 20, read 20 bytes
@@ -27,6 +29,7 @@ TEST(LocalFileReaderTest, testReadingFromFile) {
 
   EXPECT_EQ(nBytes, 20);
   IOTestHelper::expectBufferToEqualString(buf, "this is a test file\n", 20);
+  EXPECT_FALSE(reader->eof());
 
   /*
       CASE 1B
@@ -37,6 +40,7 @@ TEST(LocalFileReaderTest, testReadingFromFile) {
   EXPECT_EQ(nBytes, 25);
   IOTestHelper::expectBufferToEqualString(
       buf2, "it has many lines in it\n\n", 25);
+  EXPECT_FALSE(reader->eof());
 
   /*
       CASE 2
@@ -51,6 +55,8 @@ TEST(LocalFileReaderTest, testReadingFromFile) {
   IOTestHelper::expectBufferToEqualString(
       buf3, "the quick brown fox jumped over the lazy dog\n", 45);
 
+  EXPECT_TRUE(reader->eof());
+
   EXPECT_THROW(reader->read(buf3), std::runtime_error);
 }