Use str_item and use str_slice appropriately

Author: Smit-create

src/libasr/codegen/asr_to_llvm.cpp

@@ -1056,19 +1056,19 @@ class ASRToLLVMVisitor : public ASR::BaseVisitor<ASRToLLVMVisitor>
         return builder->CreateCall(fn, {str});
     }
 
-    llvm::Value* lfortran_str_copy(llvm::Value* str, llvm::Value* idx1, llvm::Value* idx2)
+    llvm::Value* lfortran_str_item(llvm::Value* str, llvm::Value* idx1)
     {
-        std::string runtime_func_name = "_lfortran_str_copy";
+        std::string runtime_func_name = "_lfortran_str_item";
         llvm::Function *fn = module->getFunction(runtime_func_name);
         if (!fn) {
             llvm::FunctionType *function_type = llvm::FunctionType::get(
                     character_type, {
-                        character_type, llvm::Type::getInt32Ty(context), llvm::Type::getInt32Ty(context)
+                        character_type, llvm::Type::getInt32Ty(context)
                     }, false);
             fn = llvm::Function::Create(function_type,
                     llvm::Function::ExternalLinkage, runtime_func_name, *module);
         }
-        return builder->CreateCall(fn, {str, idx1, idx2});
+        return builder->CreateCall(fn, {str, idx1});
     }
 
     llvm::Value* lfortran_str_slice(llvm::Value* str, llvm::Value* idx1, llvm::Value* idx2,
@@ -1827,7 +1827,7 @@ class ASRToLLVMVisitor : public ASR::BaseVisitor<ASRToLLVMVisitor>
                 std::vector<llvm::Value*> idx_vec = {idx};
                 p = CreateGEP(str, idx_vec);
             } else {
-                p = lfortran_str_copy(str, idx, idx);
+                p = lfortran_str_item(str, idx);
             }
             // TODO: Currently the string starts at the right location, but goes to the end of the original string.
             // We have to allocate a new string, copy it and add null termination.
@@ -1910,7 +1910,9 @@ class ASRToLLVMVisitor : public ASR::BaseVisitor<ASRToLLVMVisitor>
         // llvm::Value *p = CreateGEP(str, idx_vec);
         // TODO: Currently the string starts at the right location, but goes to the end of the original string.
         // We have to allocate a new string, copy it and add null termination.
-        llvm::Value *p = lfortran_str_copy(str, idx1, idx2);
+        llvm::Value *step = llvm::ConstantInt::get(context, llvm::APInt(32, 1));
+        llvm::Value *present = llvm::ConstantInt::get(context, llvm::APInt(1, 1));
+        llvm::Value *p = lfortran_str_slice(str, idx1, idx2, step, present, present);
 
         tmp = builder->CreateAlloca(character_type, nullptr);
         builder->CreateStore(p, tmp);
@@ -4784,7 +4786,7 @@ class ASRToLLVMVisitor : public ASR::BaseVisitor<ASRToLLVMVisitor>
         llvm::Value *idx = tmp;
         this->visit_expr_wrapper(x.m_arg, true);
         llvm::Value *str = tmp;
-        tmp = lfortran_str_copy(str, idx, idx);
+        tmp = lfortran_str_item(str, idx);
     }
 
     void visit_StringSection(const ASR::StringSection_t& x) {

src/libasr/runtime/lfortran_intrinsics.c

@@ -849,27 +849,20 @@ LFORTRAN_API char* _lfortran_strrepeat_c(char* s, int32_t n)
     return dest_char;
 }
 
-// idx1 and idx2 both start from 1
-LFORTRAN_API char* _lfortran_str_copy(char* s, int32_t idx1, int32_t idx2) {
+// idx starts from 1
+LFORTRAN_API char* _lfortran_str_item(char* s, int32_t idx) {
 
     int s_len = strlen(s);
-    if(idx1 > s_len || idx1 <= (-1*s_len)){
-        printf("String index out of Bounds\n");
+    int original_idx = idx - 1;
+    if (idx < 1) idx += s_len;
+    if (idx < 1 || idx >= s_len + 1) {
+        printf("String index: %d is out of Bounds\n", original_idx);
         exit(1);
     }
-    if(idx1 <= 0) {
-        idx1 = s_len + idx1;
-    }
-    if(idx2 <= 0) {
-        idx2 = s_len + idx2;
-    }
-    char* dest_char = (char*)malloc(idx2-idx1+2);
-    for (int i=idx1; i <= idx2; i++)
-    {
-        dest_char[i-idx1] = s[i-1];
-    }
-    dest_char[idx2-idx1+1] = '\0';
-    return dest_char;
+    char* res = (char*)malloc(2);
+    res[0] = s[idx-1];
+    res[1] = '\0';
+    return res;
 }
 
 LFORTRAN_API char* _lfortran_str_slice(char* s, int32_t idx1, int32_t idx2, int32_t step,

src/libasr/runtime/lfortran_intrinsics.h

@@ -168,6 +168,7 @@ LFORTRAN_API int8_t* _lfortran_realloc(int8_t* ptr, int32_t size);
 LFORTRAN_API int8_t* _lfortran_calloc(int32_t count, int32_t size);
 LFORTRAN_API void _lfortran_free(char* ptr);
 LFORTRAN_API void _lfortran_string_init(int size_plus_one, char *s);
+LFORTRAN_API char* _lfortran_str_item(char* s, int32_t idx);
 LFORTRAN_API char* _lfortran_str_slice(char* s, int32_t idx1, int32_t idx2, int32_t step,
                         bool idx1_present, bool idx2_present);
 LFORTRAN_API int32_t _lfortran_iand32(int32_t x, int32_t y);