io: add an fd overload for slurp

io.cpp

@@ -122,6 +122,57 @@ template std::vector<char> cruft::slurp (FILE*);
 template std::vector<std::byte> cruft::slurp (FILE*);
 
 
+
+///////////////////////////////////////////////////////////////////////////////
+template <typename ValueT>
+std::vector<ValueT>
+cruft::slurp (posix::fd &src)
+{
+    struct stat meta;
+    posix::error::try_value (fstat (src, &meta));
+
+    std::vector<ValueT> buf;
+
+    // we think we know the size, so try to do a simple read
+    if (meta.st_size) {
+        buf.resize (meta.st_size);
+
+        // read as much as possible, then resize to the actual length
+        auto const res = cruft::posix::error::try_call (
+            ::read, src.native (), buf.data (), meta.st_size
+        );
+        buf.resize (res);
+    }
+
+    // try reading small chunks until we've hit the end. important for
+    // handling pipe streams (like from popen) which report a zero size.
+    constexpr size_t CHUNK_SIZE = 1024;
+
+    while (1) {
+        // Make room for some more data
+        auto const oldsize = buf.size ();
+        buf.resize (oldsize + CHUNK_SIZE);
+
+        // Append the data
+        auto const res = cruft::posix::error::try_call (
+            ::read, src.native (), buf.data () + oldsize, CHUNK_SIZE
+        );
+        buf.resize (oldsize + res);
+
+        // Bail if we've hit EOF
+        if (res == 0)
+            break;
+    }
+
+    return buf;
+}
+
+
+//-----------------------------------------------------------------------------
+template std::vector<char> cruft::slurp (posix::fd&);
+template std::vector<std::byte> cruft::slurp (posix::fd&);
+
+
 //////////////////////////////////////////////////////////////////////////////
 int
 indenter::overflow (int ch) {

io.hpp

@@ -26,14 +26,32 @@
 #endif
 
 namespace cruft {
-    //-------------------------------------------------------------------------
+    ///////////////////////////////////////////////////////////////////////////
-    /// Reads an entire file into memory.
+    /// Reads an entire file into memory in one operation.
     template <typename T = std::byte>
-    std::vector<T> slurp (const std::experimental::filesystem::path&);
+    std::vector<T>
+    slurp (const std::experimental::filesystem::path&);
 
 
+    ///------------------------------------------------------------------------
+    /// Read the entire contents of a FILE object into memory.
+    ///
+    /// * This may trigger an arbitrary number of read calls.
+    /// * This may block indefinitely depending on the contents of the fd.
     template <typename T = std::byte>
-    std::vector<T> slurp (FILE *);
+    std::vector<T>
+    slurp (FILE *);
+
+
+    ///------------------------------------------------------------------------
+    /// Read the entire contents of a file-descriptor into memory in one
+    /// operation.
+    ///
+    /// * This may trigger an arbitrary number of read calls.
+    /// * This may block indefinitely depending on the contents of the fd.
+    template <typename T = std::byte>
+    std::vector<T>
+    slurp (cruft::posix::fd&);
 
 
     ///////////////////////////////////////////////////////////////////////////