Implement manifest serializer

3 files changed, 313 insertions, 1 deletions

diff --git a/bpkg/buildfile b/bpkg/buildfile
index b7c1c9f..45d9d89 100644
--- a/bpkg/buildfile
+++ b/bpkg/buildfile
@@ -2,4 +2,5 @@
 # copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
 # license   : MIT; see accompanying LICENSE file
 
-lib{bpkg}: cxx{manifest-parser}
+import libs += libhello
+lib{bpkg}: cxx{manifest-parser manifest-serializer} $libs
diff --git a/bpkg/manifest-serializer b/bpkg/manifest-serializer
new file mode 100644
index 0000000..2c5a09b
--- /dev/null
+++ b/bpkg/manifest-serializer
@@ -0,0 +1,73 @@
+// file      : bpkg/manifest-serializer -*- C++ -*-
+// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef BPKG_MANIFEST_SERIALIZER
+#define BPKG_MANIFEST_SERIALIZER
+
+#include <string>
+#include <iosfwd>
+#include <cstddef>   // size_t
+#include <stdexcept> // runtime_error
+
+namespace bpkg
+{
+  class manifest_serialization: public std::runtime_error
+  {
+  public:
+    manifest_serialization (const std::string& name,
+                            const std::string& description);
+
+    std::string name;
+    std::string description;
+  };
+
+  class manifest_serializer
+  {
+  public:
+    manifest_serializer (std::ostream& os, const std::string& name)
+        : os_ (os), name_ (name) {}
+
+    const std::string&
+    name () const {return name_;}
+
+    // The first name-value pair should be the special "start-of-manifest"
+    // with empty name and value being the format version. After that we
+    // have a sequence of ordinary pairs which are the manifest. At the
+    // end of the manifest we have the special "end-of-manifest" pair
+    // with empty name and value. After that we can either have another
+    // start-of-manifest pair (in which case the whole sequence repeats
+    // from the beginning) or we get another end-of-manifest pair which
+    // signals the end of stream.
+    //
+    void
+    next (const std::string& name, const std::string& value);
+
+    // Write a comment. The supplied text is prefixed with "# " and
+    // terminated with a newline.
+    //
+    void
+    comment (const std::string&);
+
+  private:
+    void
+    check_name (const std::string&);
+
+    // Write 'n' characters from 's' (assuming there are no newlines)
+    // split into multiple lines at or near the 78 characters
+    // boundary. The first line starts at the 'column' offset.
+    //
+    void
+    write_value (std::size_t column, const char* s, std::size_t n);
+
+  private:
+    enum {start, body, end} s_ = start;
+    std::string version_; // Current format version.
+
+  private:
+    std::ostream& os_;
+    const std::string name_;
+  };
+}
+
+#endif // BPKG_MANIFEST_SERIALIZER
diff --git a/bpkg/manifest-serializer.cxx b/bpkg/manifest-serializer.cxx
new file mode 100644
index 0000000..1d9fd89
--- /dev/null
+++ b/bpkg/manifest-serializer.cxx
@@ -0,0 +1,238 @@
+// file      : bpkg/manifest-serializer.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <bpkg/manifest-serializer>
+
+#include <ostream>
+#include <cassert>
+
+using namespace std;
+
+namespace bpkg
+{
+  using serialization = manifest_serialization;
+
+  void manifest_serializer::
+  next (const string& n, const string& v)
+  {
+    switch (s_)
+    {
+    case start:
+      {
+        if (!n.empty ())
+          throw serialization (name_, "format version pair expected");
+
+        if (v.empty ())
+        {
+          // End of manifests.
+          //
+          os_.flush ();
+          s_ = end;
+          break;
+        }
+
+        if (v != "1")
+          throw serialization (name_, "unsupported format version " + v);
+
+        os_ << ':';
+
+        if (v != version_)
+        {
+          os_ << ' ' << v;
+          version_ = v;
+        }
+
+        os_ << endl;
+        s_ = body;
+        break;
+      }
+    case body:
+      {
+        if (n.empty ())
+        {
+          if (!v.empty ())
+            throw serialization (name_, "non-empty value in end pair");
+
+          s_ = start;
+          break;
+        }
+
+        check_name (n);
+
+        os_ << n << ':';
+
+        if (!v.empty ())
+        {
+          os_ << ' ';
+
+          // Use the multi-line mode in any of the following cases:
+          //
+          // - name is too long (say longer than 37 (78/2 - 2) characters;
+          //   we cannot start on the next line since that would start the
+          //   multi-line mode)
+          // - value contains newlines
+          // - value contains leading/trailing whitespaces
+          //
+          if (n.size () > 37 ||
+              v.find ('\n') != string::npos ||
+              v.front () == ' ' || v.front () == '\t' ||
+              v.back () == ' ' || v.back () == '\t')
+          {
+            os_ << "\\" << endl; // Multi-line mode introductor.
+
+            // Chunk the value into fragments separated by newlines.
+            //
+            for (size_t i (0), p (v.find ('\n')); ; p = v.find ('\n', i))
+            {
+              if (p == string::npos)
+              {
+                // Last chunk.
+                //
+                write_value (0, v.c_str () + i, v.size () - i);
+                break;
+              }
+
+              write_value (0, v.c_str () + i, p - i);
+              os_ << endl;
+              i = p + 1;
+            }
+
+            os_ << endl << "\\"; // Multi-line mode terminator.
+          }
+          else
+            write_value (n.size () + 2, v.c_str (), v.size ());
+        }
+
+        os_ << endl;
+        break;
+      }
+    case end:
+      {
+        throw serialization (name_, "serialization after eos");
+      }
+    }
+  }
+
+  void manifest_serializer::
+  comment (const string& t)
+  {
+    if (s_ == end)
+      throw serialization (name_, "serialization after eos");
+
+    os_ << '#';
+
+    if (!t.empty ())
+      os_ << ' ' << t;
+
+    os_ << endl;
+  }
+
+  void manifest_serializer::
+  check_name (const string& n)
+  {
+    if (n[0] == '#')
+      throw serialization (name_, "name starts with '#'");
+
+    for (char c: n)
+    {
+      switch (c)
+      {
+      case ' ':
+      case '\t':
+      case '\n': throw serialization (name_, "name contains whitespace");
+      case ':': throw serialization (name_, "name contains ':'");
+      default: break;
+      }
+    }
+  }
+
+  void manifest_serializer::
+  write_value (size_t cl, const char* s, size_t n)
+  {
+    char c ('\0');
+
+    // The idea is to break on the 77th character (i.e., write it
+    // on the next line) which means we have written 76 characters
+    // on this line plus 2 for '\' and '\n', which gives us 78.
+    //
+    for (const char* e (s + n); s != e; s++, cl++)
+    {
+      c = *s;
+      bool br (false); // Break the line.
+
+      // If this is a whitespace, see if it's a good place to break the
+      // line.
+      //
+      if (c == ' ' || c == '\t')
+      {
+        // Find the next whitespace (or the end) and see if it is a better
+        // place.
+        //
+        for (const char* w (s + 1); ; w++)
+        {
+          if (w == e || *w == ' ' || *w == '\t')
+          {
+            // Is this whitespace past where we need to break? Also see
+            // below the "hard" break case for why we use 78 at the end.
+            //
+            if (cl + static_cast<size_t> (w - s) > (w != e ? 77 : 78))
+            {
+              // Only break if this whitespace is close enough to
+              // the end of the line.
+              //
+              br = (cl > 57);
+            }
+
+            break;
+          }
+        }
+      }
+
+      // Do we have to do a "hard" break (i.e., without a whitespace)?
+      // If there is just one character left, then instead of writing
+      // '\' and then the character on the next line, we might as well
+      // write it on this line.
+      //
+      if (cl == (s + 1 != e ? 77 : 78))
+        br = true;
+
+      if (br)
+      {
+        os_ << '\\' << endl;
+        cl = 0;
+      }
+
+      os_ << c;
+    }
+
+    // What comes next is always a newline. I the last character that
+    // we have written is a backslash, escape it.
+    //
+    if (c == '\\')
+      os_ << '\\';
+  }
+
+  // manifest_serialization
+  //
+
+  static string
+  format (const string& n, const string& d)
+  {
+    string r;
+    if (!n.empty ())
+    {
+      r += n;
+      r += ": ";
+    }
+    r += "error: ";
+    r += d;
+    return r;
+  }
+
+  manifest_serialization::
+  manifest_serialization (const string& n, const string& d)
+      : runtime_error (format (n, d)), name (n), description (d)
+  {
+  }
+}