diff options
Diffstat (limited to 'py')
| -rw-r--r-- | py/objstr.c | 103 |
1 files changed, 62 insertions, 41 deletions
diff --git a/py/objstr.c b/py/objstr.c index fc9dfd200b..fa658ac4d7 100644 --- a/py/objstr.c +++ b/py/objstr.c @@ -413,61 +413,82 @@ mp_obj_t str_replace(uint n_args, const mp_obj_t *args) { assert(MP_OBJ_IS_STR(args[1])); assert(MP_OBJ_IS_STR(args[2])); - int max_rep = 0; + machine_int_t max_rep = 0; if (n_args == 4) { assert(MP_OBJ_IS_SMALL_INT(args[3])); max_rep = MP_OBJ_SMALL_INT_VALUE(args[3]); if (max_rep == 0) { - return(args[0]); - } - else if (max_rep < 0) { + return args[0]; + } else if (max_rep < 0) { max_rep = 0; } } - //if max_rep is still 0 by this point we will need to do all possible replacements + + // if max_rep is still 0 by this point we will need to do all possible replacements GET_STR_DATA_LEN(args[0], str, str_len); GET_STR_DATA_LEN(args[1], old, old_len); GET_STR_DATA_LEN(args[2], new, new_len); + + // old won't exist in str if it's longer, so nothing to replace if (old_len > str_len) { - return(args[0]); - } + return args[0]; + } + + // data for the replaced string + byte *data = NULL; + mp_obj_t replaced_str = MP_OBJ_NULL; + + // do 2 passes over the string: + // first pass computes the required length of the replaced string + // second pass does the replacements + for (;;) { + machine_uint_t replaced_str_index = 0; + machine_uint_t num_replacements_done = 0; + const byte *old_occurrence; + const byte *offset_ptr = str; + machine_uint_t offset_num = 0; + while ((old_occurrence = find_subbytes(offset_ptr, str_len - offset_num, old, old_len)) != NULL) { + // copy from just after end of last occurrence of to-be-replaced string to right before start of next occurrence + if (data != NULL) { + memcpy(data + replaced_str_index, offset_ptr, old_occurrence - offset_ptr); + } + replaced_str_index += old_occurrence - offset_ptr; + // copy the replacement string + if (data != NULL) { + memcpy(data + replaced_str_index, new, new_len); + } + replaced_str_index += new_len; + offset_ptr = old_occurrence + old_len; + offset_num = offset_ptr - str; - size_t required_len = 0; - const byte *old_occurrence; - const byte *offset_ptr = str; - size_t offset_num = 0; - while((old_occurrence = find_subbytes(offset_ptr, str_len - offset_num, old, old_len)) != NULL){ - required_len += old_occurrence - offset_ptr; - required_len += new_len; - offset_ptr = old_occurrence + old_len; - offset_num = offset_ptr - str; - } - required_len += str_len - offset_num; - byte *data; - mp_obj_t replaced_str = mp_obj_str_builder_start(mp_obj_get_type(args[0]), required_len, &data); - - size_t replaced_str_index = 0; - int replacements_done = 0; - offset_ptr = str; - offset_num = 0; - while((old_occurrence = find_subbytes(offset_ptr, str_len - offset_num, old, old_len)) != NULL){ - //copy from just after end of last occurrence of to-be-replaced string to right before start of next occurrence - memcpy(data + replaced_str_index, offset_ptr, old_occurrence - offset_ptr); - replaced_str_index += old_occurrence - offset_ptr; - //copy the replacement string - memcpy(data + replaced_str_index, new, new_len); - replaced_str_index += new_len; - offset_ptr = old_occurrence + old_len; - offset_num = offset_ptr - str; - - replacements_done++; - if (max_rep != 0 && replacements_done == max_rep){ - break; - } + num_replacements_done++; + if (max_rep != 0 && num_replacements_done == max_rep){ + break; + } + } + + // copy from just after end of last occurrence of to-be-replaced string to end of old string + if (data != NULL) { + memcpy(data + replaced_str_index, offset_ptr, str_len - offset_num); + } + replaced_str_index += str_len - offset_num; + + if (data == NULL) { + // first pass + if (num_replacements_done == 0) { + // no substr found, return original string + return args[0]; + } else { + // substr found, allocate new string + replaced_str = mp_obj_str_builder_start(mp_obj_get_type(args[0]), replaced_str_index, &data); + } + } else { + // second pass, we are done + break; + } } - //copy from just after end of last occurrence of to-be-replaced string to end of old string - memcpy(data + replaced_str_index, offset_ptr, str_len - offset_num); + return mp_obj_str_builder_end(replaced_str); } |