ChatON: Initial go at chat-template-apply c-api with parts info

common/chaton.hpp

@@ -541,6 +541,7 @@ inline int32_t chaton_tmpl_apply(
 // If the passed char array is smaller than that required for the tagged messages string,
 // * part of the tagged messages string which fits within dest buffer is copied
 // * the returned value, indicates the size of the actual tagged message
+//
 // NOTE:
 // * ideally the passed char array should be able to fit the tagged messages string + 0|null char.
 // * if the return value from this function is larger than or equal to destLength,
@@ -572,6 +573,58 @@ inline int32_t chaton_tmpl_apply_capi(
     return taggedLength;
 }
 
+//
+// In addition to the semantic provided by chaton_tmpl_apply_capi
+// this additionally also returns info about the parts that make up
+// the returned tagged message.
+//
+// partTypes and partLengths should be arrays that can accomodate the
+// same number of elements belonging to its respective type.
+// Inturn the pNumParts should point to a int which specifies the
+// number of elements.
+// If the generated tagged message has more parts than the specified
+// *pNumParts, then the logic copies partTypes and partLengths to the
+// specified length/NumOfParts only. Parallely it updates *pNumParts
+// to the actual needed length (not including any terminating null char or so).
+//
+inline int32_t chaton_tmpl_apply_ex_capi(
+        const char *tmpl,
+        const struct llama_chat_message *msgs,
+        const size_t numMsgs,
+        bool alertAssistantAtEnd,
+        char *dest,
+        int32_t destLength,
+        char *partTypes,
+        int32_t *partLengths,
+        int32_t *pNumParts
+        ) {
+    if ((tmpl == nullptr) || (dest == nullptr)) {
+        return -1;
+    }
+    std::vector<const llama_chat_message *> vMsgs;
+    for(size_t i=0; i<numMsgs; i++) {
+        vMsgs.push_back(&msgs[i]);
+    }
+    std::string taggedMsgs;
+    std::string types;
+    std::vector<int> lens;
+    int32_t taggedLength = chaton_tmpl_apply_ex(tmpl, vMsgs, taggedMsgs, types, lens, alertAssistantAtEnd);
+    if (taggedLength <= 0) {
+        return taggedLength;
+    }
+    if (destLength > 0) {
+        strlcpy(dest, taggedMsgs.c_str(), destLength);
+    }
+    if (*pNumParts > 0) {
+        strlcpy(partTypes, types.c_str(), *pNumParts);
+        for(int i=0; i < *pNumParts; i++) {
+            partLengths[i] = lens[i];
+        }
+    }
+    *pNumParts = types.length();
+    return taggedLength;
+}
+
 
 /**
  * if tmpl is