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Patrick Monnerat 92e6782d1f doc: some returned in-memory data may not be altered

Some public prototypes do not declare return values or out parameters as
const where they should be. Avoid changing the public interface, but
document those values as read-only.

Closes #19692

2025-11-25 11:05:27 +01:00

1.9 KiB

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c, SPDX-License-Identifier, Title, Section, Source, See-also, Protocol, Added-in

SPDX-License-Identifier

Title

Section

Source

See-also

Protocol

Added-in

curl

curl_easy_unescape

libcurl

curl_easy_escape (3)

curl_url_get (3)

All

7.15.4

NAME

curl_easy_unescape - URL decode a string

SYNOPSIS

#include <curl/curl.h>

char *curl_easy_unescape(CURL *curl, const char *input,
                         int inlength, int *outlength);

DESCRIPTION

This function converts the URL encoded string input to a "plain string" and returns that in an allocated memory area. All input characters that are URL encoded (%XX where XX is a two-digit hexadecimal number) are converted to their binary versions. Although not constrained by its type, the returned data may not be altered.

If the length argument is set to 0 (zero), curl_easy_unescape(3) uses strlen() on input to find out the size.

If outlength is non-NULL, the function writes the length of the returned string in the integer it points to. This allows proper handling even for strings containing %00. Since this is a pointer to an int type, it can only return a value up to INT_MAX so no longer string can be returned in this parameter.

Since 7.82.0, the curl parameter is ignored. Prior to that there was per-handle character conversion support for some old operating systems such as TPF, but it was otherwise ignored.

You must curl_free(3) the returned string when you are done with it.

%PROTOCOLS%

EXAMPLE

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    int decodelen;
    char *decoded = curl_easy_unescape(curl, "%63%75%72%6c", 12, &decodelen);
    if(decoded) {
      /* do not assume printf() works on the decoded data */
      printf("Decoded: ");
      /* ... */
      curl_free(decoded);
    }
    curl_easy_cleanup(curl);
  }
}

%AVAILABILITY%

RETURN VALUE

A pointer to a null-terminated string or NULL if it failed.

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