[ADD/WIP] Basic XEP-0393 support.

Still needs lots of work. Did I fail to mention I _hate_ HTML?

src/Streams/Reader.c

@@ -0,0 +1,131 @@
+#include <StringStream.h>
+
+#include <Cytoplasm/Memory.h>
+#include <Cytoplasm/Stream.h>
+#include <Cytoplasm/Str.h>
+#include <Cytoplasm/Io.h>
+
+#include <string.h>
+
+typedef struct ReaderCookie {
+    size_t length;
+    size_t offset;
+    char *buffer;
+} ReaderCookie;
+
+#define Remaining() (cook->length - cook->offset)
+
+static ssize_t
+ReadStreamReader(void *coop, void *to, size_t n)
+{
+    ReaderCookie *cook = coop;
+    size_t remaining;
+    if (!cook)
+    {
+        return 0;
+    }
+
+    remaining = Remaining();
+    if (n > remaining)
+    {
+        memcpy(to, cook->buffer + cook->offset, remaining);
+        cook->offset = cook->length;
+        return remaining;
+    }
+
+    memcpy(to, cook->buffer + cook->offset, n);
+    cook->offset += n;
+    return n;
+}
+static ssize_t
+WriteStreamReader(void *coop, void *from, size_t n)
+{
+    /* Writing to a stream reader is silly. */
+    return 0;
+}
+static off_t
+SeekStreamReader(void *coop, off_t mag, int sgn)
+{
+    ReaderCookie *cook = coop;
+    if (!cook)
+    {
+        return 0;
+    }
+
+    switch (sgn)
+    {
+        case SEEK_SET:
+            if (mag > cook->length)
+            {
+                cook->offset = cook->length;
+                return 0;
+            }
+            else if (mag < 0)
+            {
+                cook->offset = 0;
+                return 0;
+            }
+            cook->offset = mag;
+            return 0;
+        case SEEK_CUR:
+            cook->offset += mag;
+            if (cook->offset > cook->length)
+            {
+                cook->offset = cook->length;
+            }
+            else if (cook->offset < 0)
+            {
+                cook->offset = 0;
+            }
+            return 0;
+        case SEEK_END:
+            cook->offset += cook->length + mag;
+            if (cook->offset > cook->length)
+            {
+                cook->offset = cook->length;
+            }
+            else if (cook->offset < 0)
+            {
+                cook->offset = 0;
+            }
+            return 0;
+            
+    }
+    return 0;
+}
+
+static int
+CloseStreamReader(void *coop)
+{
+    /* Nothing to free as of now. */
+    if (coop)
+    {
+        Free(coop);
+    }
+    return 0;
+}
+
+const static IoFunctions Functions = {
+    .read   = ReadStreamReader,
+    .seek   = SeekStreamReader,
+    .write  = WriteStreamReader,
+    .close  = CloseStreamReader,
+};
+
+Stream *
+StrStreamReader(char *buffer)
+{
+    Io *raw_io;
+    ReaderCookie *cookie;
+    if (!buffer)
+    {
+        return NULL;
+    }
+
+    cookie = Malloc(sizeof(*cookie));
+    cookie->buffer = buffer;
+    cookie->length = strlen(buffer);
+    cookie->offset = 0;
+    raw_io = IoCreate(cookie, Functions);
+    return StreamIo(raw_io);
+}