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vim-patch:9.2.0351: repeat_string() can be improved (#39101)

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Problem:  repeat_string() can be improved
Solution: Replace the for() loop by an exponential growing while loop
          (Yasuhiro Matsumoto)

closes: vim/vim#19977

bfa46a52f6

Cherry-pick f_repeat() refactor from patch 9.1.1232.

Co-authored-by: Yasuhiro Matsumoto <mattn.jp@gmail.com>
This commit is contained in:
zeertzjq
2026-04-16 11:11:04 +08:00
committed by GitHub
parent a90c3e382d
commit 8af2ba74a4
1 changed files with 86 additions and 58 deletions
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144
src/nvim/eval/funcs.c
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@@ -5290,71 +5290,99 @@ static void f_reltimestr(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
}
}
/// Repeat the list "l" "n" times and set "rettv" to the new list.
static void repeat_list(list_T *l, varnumber_T n, typval_T *rettv)
{
tv_list_alloc_ret(rettv, (n > 0) * n * tv_list_len(l));
while (n-- > 0) {
tv_list_extend(rettv->vval.v_list, l, NULL);
}
}
/// Repeat the blob "b" "n" times and set "rettv" to the new blob.
static void repeat_blob(typval_T *blob_tv, varnumber_T n, typval_T *rettv)
{
blob_T *const blob = blob_tv->vval.v_blob;
tv_blob_alloc_ret(rettv);
if (blob == NULL || n <= 0) {
return;
}
const int slen = blob->bv_ga.ga_len;
const int len = (int)(slen * n);
if (len <= 0) {
return;
}
ga_grow(&rettv->vval.v_blob->bv_ga, len);
rettv->vval.v_blob->bv_ga.ga_len = len;
int i;
for (i = 0; i < slen; i++) {
if (tv_blob_get(blob, i) != 0) {
break;
}
}
if (i == slen) {
// No need to copy since all bytes are already zero
return;
}
for (i = 0; i < n; i++) {
tv_blob_set_range(rettv->vval.v_blob, i * slen, (i + 1) * slen - 1, blob_tv);
}
}
/// Repeat the string "str" "n" times and set "rettv" to the new string.
static void repeat_string(typval_T *str_tv, varnumber_T n, typval_T *rettv)
{
rettv->v_type = VAR_STRING;
rettv->vval.v_string = NULL;
if (n <= 0) {
return;
}
const char *const p = tv_get_string(str_tv);
const size_t slen = strlen(p);
if (slen == 0) {
return;
}
const size_t len = slen * (size_t)n;
// Detect overflow.
if (len / (size_t)n != slen) {
return;
}
char *const r = xmallocz(len);
memmove(r, p, slen);
size_t done = slen;
while (done < len) {
size_t copy_len = done;
if (copy_len > len - done) {
copy_len = len - done;
}
memmove(r + done, r, copy_len);
done += copy_len;
}
rettv->vval.v_string = r;
}
/// "repeat()" function
static void f_repeat(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
{
varnumber_T n = tv_get_number(&argvars[1]);
if (argvars[0].v_type == VAR_LIST) {
tv_list_alloc_ret(rettv, (n > 0) * n * tv_list_len(argvars[0].vval.v_list));
while (n-- > 0) {
tv_list_extend(rettv->vval.v_list, argvars[0].vval.v_list, NULL);
}
repeat_list(argvars[0].vval.v_list, n, rettv);
} else if (argvars[0].v_type == VAR_BLOB) {
tv_blob_alloc_ret(rettv);
if (argvars[0].vval.v_blob == NULL || n <= 0) {
return;
}
const int slen = argvars[0].vval.v_blob->bv_ga.ga_len;
const int len = (int)(slen * n);
if (len <= 0) {
return;
}
ga_grow(&rettv->vval.v_blob->bv_ga, len);
rettv->vval.v_blob->bv_ga.ga_len = len;
int i;
for (i = 0; i < slen; i++) {
if (tv_blob_get(argvars[0].vval.v_blob, i) != 0) {
break;
}
}
if (i == slen) {
// No need to copy since all bytes are already zero
return;
}
for (i = 0; i < n; i++) {
tv_blob_set_range(rettv->vval.v_blob, i * slen, (i + 1) * slen - 1, argvars);
}
repeat_blob(&argvars[0], n, rettv);
} else {
rettv->v_type = VAR_STRING;
rettv->vval.v_string = NULL;
if (n <= 0) {
return;
}
const char *const p = tv_get_string(&argvars[0]);
const size_t slen = strlen(p);
if (slen == 0) {
return;
}
const size_t len = slen * (size_t)n;
// Detect overflow.
if (len / (size_t)n != slen) {
return;
}
char *const r = xmallocz(len);
for (varnumber_T i = 0; i < n; i++) {
memmove(r + (size_t)i * slen, p, slen);
}
rettv->vval.v_string = r;
repeat_string(&argvars[0], n, rettv);
}
}