StrLib: add AsciiGetString and AsciiGetNextString

this allows iterating over single-buffer string-arrays
like the ones used by fdt blobs.

Include/Library/StrLib.h

@@ -1,11 +1,32 @@
 #ifndef __LIBRARY_STR_H__
 #define __LIBRARY_STR_H__
 
+typedef struct {
+  CONST CHAR8 *Current;
+  CONST CHAR8 *End;
+} ASCII_GETSTRING_STATE;
+
 CHAR8 *strtok(CHAR8 *s, CONST CHAR8 *delim);
 CHAR8 *strtok_r(CHAR8 *s, CONST CHAR8 *delim, CHAR8 **last);
 UINTN strlcat(CHAR8 *dst, CONST CHAR8 *src, UINTN siz);
 UINTN strspn(CHAR8 CONST *s, CHAR8 CONST *accept);
 CHAR8 *strchr(CONST CHAR8 *s, INTN c);
 CHAR8 *strpbrk(CONST CHAR8 *s, CONST CHAR8 *accept);
 
+RETURN_STATUS
+EFIAPI
+AsciiGetNextString (
+  IN OUT ASCII_GETSTRING_STATE   *State,
+  OUT    CONST CHAR8             **String
+  );
+
+RETURN_STATUS
+EFIAPI
+AsciiGetString (
+  IN     CONST CHAR8             *StringArray,
+  IN     UINTN                   MaxSize,
+  IN OUT ASCII_GETSTRING_STATE   *State,
+  OUT    CONST CHAR8             **String
+  );
+
 #endif

Library/StrLib/StrLib.inf

@@ -14,6 +14,8 @@
   strchr.c
   strpbrk.c
 
+  getstring.c
+
 [Packages]
   MdePkg/MdePkg.dec
   EFIDroidPkg/EFIDroidPkg.dec

Library/StrLib/getstring.c

@@ -0,0 +1,39 @@
+#include <Library/BaseLib.h>
+#include <Library/StrLib.h>
+
+RETURN_STATUS
+EFIAPI
+AsciiGetNextString (
+  IN OUT ASCII_GETSTRING_STATE   *State,
+  OUT    CONST CHAR8             **String
+  )
+{
+  if (State->Current >= State->End) {
+    return RETURN_NOT_FOUND;
+  }
+
+  UINTN CurrentLength = AsciiStrnSizeS(State->Current, State->End - State->Current);
+  if (State->Current + CurrentLength > State->End) {
+    return RETURN_UNSUPPORTED;
+  }
+
+  *String = State->Current;
+  State->Current += CurrentLength;
+
+  return RETURN_SUCCESS;
+}
+
+RETURN_STATUS
+EFIAPI
+AsciiGetString (
+  IN     CONST CHAR8             *StringArray,
+  IN     UINTN                   MaxSize,
+  IN OUT ASCII_GETSTRING_STATE   *State,
+  OUT    CONST CHAR8             **String
+  )
+{
+  State->Current = StringArray;
+  State->End = StringArray + MaxSize;
+
+  return AsciiGetNextString(State, String);
+}