Create utility method to generate file manifests

Refs: #3431

Change-Id: I1a0f06b87689e71349b4fa9346ebc29e785d86cc
diff --git a/src/file-manifest.cpp b/src/file-manifest.cpp
index fe4fec8..71ba3a6 100644
--- a/src/file-manifest.cpp
+++ b/src/file-manifest.cpp
@@ -20,11 +20,23 @@
 */
 #include "file-manifest.hpp"
 
+#include <limits>
+
 #include <boost/assert.hpp>
+#include <boost/filesystem.hpp>
+#include <boost/filesystem/fstream.hpp>
+#include <boost/lexical_cast.hpp>
 #include <boost/range/adaptors.hpp>
+#include <boost/range/irange.hpp>
 #include <boost/throw_exception.hpp>
+#include <ndn-cxx/security/key-chain.hpp>
+#include <ndn-cxx/security/signing-helpers.hpp>
 
 using std::vector;
+using std::streamsize;
+using boost::irange;
+
+namespace fs = boost::filesystem;
 
 namespace ndn {
 namespace ntorrent {
@@ -35,6 +47,168 @@
 static_assert(std::is_base_of<Data::Error, FileManifest::Error>::value,
                 "FileManifest::Error should inherit from Data::Error");
 
+static ndn::Name
+get_name_of_manifest(const std::string& filePath, const Name& manifestPrefix)
+{
+  Name full_path(fs::system_complete(filePath).string());
+  // Search the filePath for the leading component that matches
+  auto name_component_iter = std::find(full_path.rbegin(),
+                                       full_path.rend(),
+                                       *manifestPrefix.rbegin());
+
+  if (full_path.rend() == name_component_iter) {
+    BOOST_THROW_EXCEPTION(FileManifest::Error("No matching name component between" +
+                                              manifestPrefix.toUri() + " and "     +
+                                              full_path.toUri()));
+  }
+  ndn::Name manifestName;
+  // Rebuild the name to be the suffix from the matching component
+  for (auto it = (name_component_iter.base() - 1); full_path.end() != it; ++it) {
+    manifestName.append(*it);
+  }
+  return manifestName;
+}
+
+static std::vector<Data>
+packetize_file(const fs::path& filePath,
+               const ndn::Name& commonPrefix,
+               size_t dataPacketSize,
+               size_t subManifestSize,
+               size_t subManifestNum)
+{
+  BOOST_ASSERT(0 < dataPacketSize);
+  size_t APPROX_BUFFER_SIZE = std::numeric_limits<int>::max(); // 2 * 1024 * 1024 *1024
+  auto file_size = fs::file_size(filePath);
+  auto start_offset = subManifestNum * subManifestSize * dataPacketSize;
+  // determine the number of bytes in this submanifest
+  auto subManifestLength = subManifestSize * dataPacketSize;
+  auto remainingFileLength = file_size - start_offset;
+  subManifestLength = remainingFileLength < subManifestLength
+                    ? remainingFileLength
+                    : subManifestLength;
+  std::vector<Data> packets;
+  packets.reserve(subManifestLength/dataPacketSize + 1);
+  fs::ifstream fs(filePath, fs::ifstream::binary);
+  if (!fs) {
+    BOOST_THROW_EXCEPTION(FileManifest::Error("IO Error when opening" + filePath.string()));
+  }
+  // ensure that buffer is large enough to contain whole packets
+  // buffer size is either the entire file or the smallest number of data packets >= 2 GB
+  auto buffer_size =
+    subManifestLength < APPROX_BUFFER_SIZE   ?
+    subManifestLength                        :
+    APPROX_BUFFER_SIZE % dataPacketSize == 0 ?
+    APPROX_BUFFER_SIZE :
+    APPROX_BUFFER_SIZE + dataPacketSize - (APPROX_BUFFER_SIZE % dataPacketSize);
+  std::vector<char> file_bytes;
+  file_bytes.reserve(buffer_size);
+  size_t bytes_read = 0;
+  fs.seekg(start_offset);
+  while(fs && bytes_read < subManifestLength && !fs.eof()) {
+    // read the file into the buffer
+    fs.read(&file_bytes.front(), buffer_size);
+    auto read_size = fs.gcount();
+    if (fs.bad() || read_size < 0) {
+
+      BOOST_THROW_EXCEPTION(FileManifest::Error("IO Error when reading" + filePath.string()));
+    }
+    bytes_read += read_size;
+    char *curr_start = &file_bytes.front();
+    for (size_t i = 0u; i < buffer_size; i += dataPacketSize) {
+      // Build a packet from the data
+      Name packetName = commonPrefix;
+      packetName.appendSequenceNumber(packets.size());
+      Data d(packetName);
+      auto content_length = i + dataPacketSize > buffer_size ? buffer_size - i : dataPacketSize;
+      d.setContent(encoding::makeBinaryBlock(tlv::Content, curr_start, content_length));
+      curr_start += content_length;
+      // append to the collection
+      packets.push_back(d);
+    }
+    file_bytes.clear();
+    // recompute the buffer_size
+    buffer_size =
+      subManifestLength - bytes_read < APPROX_BUFFER_SIZE ?
+      subManifestLength - bytes_read                      :
+      APPROX_BUFFER_SIZE % dataPacketSize == 0            ?
+      APPROX_BUFFER_SIZE                                  :
+      APPROX_BUFFER_SIZE + dataPacketSize - (APPROX_BUFFER_SIZE % dataPacketSize);
+  }
+  fs.close();
+  packets.shrink_to_fit();
+  security::KeyChain key_chain;
+  // sign all the packets
+  for (auto& p : packets) {
+    key_chain.sign(p, signingWithSha256());
+  }
+  return packets;
+}
+
+// CLASS METHODS
+std::pair<std::vector<FileManifest>, std::vector<Data>>
+FileManifest::generate(const std::string& filePath,
+                       const Name&        manifestPrefix,
+                       size_t             subManifestSize,
+                       size_t             dataPacketSize,
+                       bool               returnData)
+{
+  BOOST_ASSERT(0 < subManifestSize);
+  BOOST_ASSERT(0 < dataPacketSize);
+  std::vector<FileManifest> manifests;
+  fs::path path(filePath);
+  if (!fs::exists(path)) {
+    BOOST_THROW_EXCEPTION(Error(filePath + ": no such file."));
+  }
+  size_t file_length = fs::file_size(filePath);
+  // If the file_length is not evenly divisible by subManifestSize add 1, otherwise 0
+  size_t numSubManifests = file_length / (subManifestSize * dataPacketSize) +
+                              !!(file_length % (subManifestSize * dataPacketSize));
+  // Find the prefix for the Catalog
+  auto manifestName = get_name_of_manifest(filePath, manifestPrefix);
+  std::vector<Data> allPackets;
+  if (returnData) {
+    allPackets.reserve(numSubManifests * subManifestSize);
+  }
+  manifests.reserve(numSubManifests);
+  for (auto subManifestNum : irange<size_t>(0, numSubManifests)) {
+    auto curr_manifest_name = manifestName;
+    curr_manifest_name.append("manifest" + boost::lexical_cast<std::string>(subManifestNum));
+    // append the packet number
+    curr_manifest_name.appendSequenceNumber(manifests.size());
+    auto subManifestPrefix = manifestPrefix;
+    subManifestPrefix.appendNumber(subManifestNum);
+    FileManifest curr_manifest(curr_manifest_name, dataPacketSize, manifestPrefix);
+    auto packets = packetize_file(path,
+                                  subManifestPrefix,
+                                  dataPacketSize,
+                                  subManifestSize,
+                                  subManifestNum);
+    if (returnData) {
+      allPackets.insert(allPackets.end(), packets.begin(), packets.end());
+    }
+    curr_manifest.reserve(packets.size());
+    // Collect all the Data packets into the sub-manifests
+    for (const auto& p: packets) {
+      curr_manifest.push_back(p.getFullName());
+    }
+    // append the last manifest
+    manifests.push_back(curr_manifest);
+  }
+  allPackets.shrink_to_fit();
+  manifests.shrink_to_fit();
+  // Set all the submanifest_ptrs and sign all the manifests
+  security::KeyChain key_chain;
+  manifests.back().finalize();
+  key_chain.sign(manifests.back(), signingWithSha256());
+  for (auto it = manifests.rbegin() + 1; it != manifests.rend(); ++it) {
+    auto next = it - 1;
+    it->set_submanifest_ptr(std::make_shared<Name>(next->getFullName()));
+    it->finalize();
+    key_chain.sign(*it, signingWithSha256());
+  }
+  return {manifests, allPackets};
+}
+
 void
 FileManifest::wireDecode(const Block& wire)
 {
@@ -72,7 +246,7 @@
   suffixCatalog.reserve(m_catalog.size());
   for (auto name: m_catalog) {
     if (!m_catalogPrefix.isPrefixOf(name)) {
-      BOOST_THROW_EXCEPTION(Error(name.toUri() + "does not have the prefix"
+      BOOST_THROW_EXCEPTION(Error(name.toUri() + " does not have the prefix "
                                                + m_catalogPrefix.toUri()));
     }
     name = name.getSubName(m_catalogPrefix.size());
@@ -106,12 +280,13 @@
 {
   BOOST_ASSERT(name != m_catalogPrefix);
   BOOST_ASSERT(m_catalogPrefix.isPrefixOf(name));
-  m_catalog.push_back(name);
+  // TODO(msweatt) Change this to use the copy constructor once bug fixed in Name()
+  m_catalog.push_back(name.toUri());
 }
 
 bool
 FileManifest::remove(const ndn::Name& name) {
-  auto it = std::find(m_catalog.begin(), m_catalog.end(), name);
+  const auto it = std::find(m_catalog.begin(), m_catalog.end(), name);
   if (m_catalog.end() == it) {
     return false;
   }