From 8ba89f5b3b3421b366e6a203d920b54ce87403d2 Mon Sep 17 00:00:00 2001
From: Emil Hvitfeldt <emilhhvitfeldt@gmail.com>
Date: Mon, 29 Apr 2024 12:45:06 -0700
Subject: [PATCH] use R_xlen_t in loops

---
 src/altrep-sparse-real.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/altrep-sparse-real.c b/src/altrep-sparse-real.c
index 3d55ab7..5972ced 100644
--- a/src/altrep-sparse-real.c
+++ b/src/altrep-sparse-real.c
@@ -66,11 +66,13 @@ static SEXP altrep_sparse_real_Extract_subset(SEXP x, SEXP indx, SEXP call) {
   SEXP data1 = R_altrep_data1(x);
   SEXP val_old = VECTOR_ELT(data1, 0);
   SEXP pos_old = VECTOR_ELT(data1, 1);
+  
   SEXP matches = PROTECT(Rf_match(pos_old, indx, R_NaInt));
+  R_xlen_t n_matches = Rf_xlength(matches);
 
   int n = 0;
 
-  for (int i = 0; i < Rf_length(matches); ++i) { 
+  for (R_xlen_t i = 0; i < n_matches; ++i) { 
     if (INTEGER_ELT(matches, i) != R_NaInt) {
       n++;
     }
@@ -82,13 +84,13 @@ static SEXP altrep_sparse_real_Extract_subset(SEXP x, SEXP indx, SEXP call) {
   int step = 0;
   int what_pos = 1;
 
-  for (int i = 0; i < Rf_length(matches); ++i) {
+  for (R_xlen_t i = 0; i < n_matches; ++i) {
 
     int match = INTEGER_ELT(matches, i);
     if (match != R_NaInt) {
       SET_REAL_ELT(val_new, step, REAL_ELT(val_old, match - 1));
 
-      for (int j = 0; j < Rf_length(matches); ++j) {
+      for (R_xlen_t j = 0; j < n_matches; ++j) {
         if (INTEGER_ELT(indx, j) == INTEGER_ELT(pos_old, match - 1)) {
           break;
         } else {
@@ -151,7 +153,7 @@ static double altrep_sparse_real_Elt(SEXP x, R_xlen_t i) {
 
   double out = 0;
 
-  for (int j = 0; j < n; ++j) {
+  for (R_xlen_t j = 0; j < n; ++j) {
     if (INTEGER_ELT(pos, j) == i + 1) {
       out = REAL_ELT(val, j);
       break;