GLib Reference Manual
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# Strings

## Name

Strings -- text buffers which grow automatically as text is added.

## Synopsis

    #include <glib.h>

    struct      GString;
    GString*    g_string_new                    (const gchar *init);
    GString*    g_string_new_len                (const gchar *init,
                                                 gssize len);
    GString*    g_string_sized_new              (gsize dfl_size);
    GString*    g_string_assign                 (GString *string,
                                                 const gchar *rval);
    #define     g_string_sprintf
    #define     g_string_sprintfa
    void        g_string_printf                 (GString *string,
                                                 const gchar *format,
                                                 ...);
    void        g_string_append_printf          (GString *string,
                                                 const gchar *format,
                                                 ...);
    GString*    g_string_append                 (GString *string,
                                                 const gchar *val);
    GString*    g_string_append_c               (GString *string,
                                                 gchar c);
    GString*    g_string_append_unichar         (GString *string,
                                                 gunichar wc);
    GString*    g_string_append_len             (GString *string,
                                                 const gchar *val,
                                                 gssize len);
    GString*    g_string_prepend                (GString *string,
                                                 const gchar *val);
    GString*    g_string_prepend_c              (GString *string,
                                                 gchar c);
    GString*    g_string_prepend_unichar        (GString *string,
                                                 gunichar wc);
    GString*    g_string_prepend_len            (GString *string,
                                                 const gchar *val,
                                                 gssize len);
    GString*    g_string_insert                 (GString *string,
                                                 gssize pos,
                                                 const gchar *val);
    GString*    g_string_insert_c               (GString *string,
                                                 gssize pos,
                                                 gchar c);
    GString*    g_string_insert_unichar         (GString *string,
                                                 gssize pos,
                                                 gunichar wc);
    GString*    g_string_insert_len             (GString *string,
                                                 gssize pos,
                                                 const gchar *val,
                                                 gssize len);
    GString*    g_string_erase                  (GString *string,
                                                 gssize pos,
                                                 gssize len);
    GString*    g_string_truncate               (GString *string,
                                                 gsize len);
    GString*    g_string_set_size               (GString *string,
                                                 gsize len);
    gchar*      g_string_free                   (GString *string,
                                                 gboolean free_segment);

    GString*    g_string_up                     (GString *string);
    GString*    g_string_down                   (GString *string);

    guint       g_string_hash                   (const GString *str);
    gboolean    g_string_equal                  (const GString *v,
                                                 const GString *v2);

## Description

A GString is similar to a standard C string, except that it grows automatically as text is appended or inserted. Also, it stores the length of the string, so can be used for binary data with embedded nul bytes.

## Details

### struct GString

    struct GString
    {
      gchar  *str;
      gsize len;
      gsize allocated_len;
    };

The GString struct contains the public fields of a GString. The `str` field points to the character data. It may move as text is added. The `len` field contains the length of the string, not including the terminating nul character.

The `str` field is nul-terminated and so can be used as an ordinary C string. But it may be moved when text is appended or inserted into the string.

### g_string_new ()

    GString*    g_string_new                    (const gchar *init);

Creates a new GString, initialized with the given string.

`init` : | the initial text to copy into the string.
Returns : | the new GString.

### g_string_new_len ()

    GString*    g_string_new_len                (const gchar *init,
                                                 gssize len);

Creates a new GString with `len` bytes of the `init` buffer. Because a length is provided, `init` need not be nul-terminated, and can contain embedded nul bytes.

`init` : | initial contents of string.
`len` : | length of `init` to use.
Returns : | a new GString.

### g_string_sized_new ()

    GString*    g_string_sized_new              (gsize dfl_size);

Creates a new GString, with enough space for `dfl_size` characters. This is useful if you are going to add a lot of text to the string and don't want it to be reallocated too often.

`dfl_size` : | the default size of the space allocated to hold the string.
Returns : | the new GString.

### g_string_assign ()

    GString*    g_string_assign                 (GString *string,
                                                 const gchar *rval);

Copies the characters from a string into a GString, destroying any previous contents. It is rather like the standard `strcpy()` function, except that you do not have to worry about having enough space to copy the string.

`string` : | the destination GString. Its current contents are destroyed.
`rval` : |
Returns : | the destination GString.

### g_string_sprintf

    #define     g_string_sprintf

Warning
`g_string_sprintf` is deprecated and should not be used in newly-written code.

Writes a formatted string into a GString. This is similar to the standard `sprintf()` function, except that the GString buffer automatically expands to contain the results. The previous contents of the GString are destroyed. This function has been renamaed to g_string_printf().

### g_string_sprintfa

    #define     g_string_sprintfa

Warning
`g_string_sprintfa` is deprecated and should not be used in newly-written code.

Appends a formatted string onto the end of a GString. This function is is similar to g_string_sprintf() except that the text is appended to the GString. The function has been renamed to g_string_append_printf().

### g_string_printf ()

    void        g_string_printf                 (GString *string,
                                                 const gchar *format,
                                                 ...);

Writes a formatted string into a GString. This is similar to the standard `sprintf()` function, except that the GString buffer automatically expands to contain the results. The previous contents of the GString are destroyed.

`string` : | a GString.
`format` : | the string format. See the `printf()` documentation.
`...` : | the parameters to insert into the format string.

### g_string_append_printf ()

    void        g_string_append_printf          (GString *string,
                                                 const gchar *format,
                                                 ...);

Appends a formatted string onto the end of a GString. This function is is similar to g_string_printf() except that the text is appended to the GString.

`string` : | a GString.
`format` : | the string format. See the `printf()` documentation.
`...` : | the parameters to insert into the format string.

### g_string_append ()

    GString*    g_string_append                 (GString *string,
                                                 const gchar *val);

Adds a string onto the end of a GString, expanding it if necessary.

`string` : | a GString.
`val` : | the string to append onto the end of the GString.
Returns : | the GString.

### g_string_append_c ()

    GString*    g_string_append_c               (GString *string,
                                                 gchar c);

Adds a character onto the end of a GString, expanding it if necessary.

`string` : | a GString.
`c` : | the character to append onto the end of the GString.
Returns : | the GString.

### g_string_append_unichar ()

    GString*    g_string_append_unichar         (GString *string,
                                                 gunichar wc);

Converts a Unicode character into UTF-8, and appends it to the string.

`string` : | a GString
`wc` : | a Unicode character
Returns : | `string`

### g_string_append_len ()

    GString*    g_string_append_len             (GString *string,
                                                 const gchar *val,
                                                 gssize len);

Appends `len` bytes of `val` to `string`. Because `len` is provided, `val` may contain embedded nuls and need not be nul-terminated.

`string` : | a GString.
`val` : | bytes to append.
`len` : | number of bytes of `val` to use.
Returns : | the GString.

### g_string_prepend ()

    GString*    g_string_prepend                (GString *string,
                                                 const gchar *val);

Adds a string on to the start of a GString, expanding it if necessary.

`string` : | a GString.
`val` : | the string to prepend on the start of the GString.
Returns : | the GString.

### g_string_prepend_c ()

    GString*    g_string_prepend_c              (GString *string,
                                                 gchar c);

Adds a character onto the start of a GString, expanding it if necessary.

`string` : | a GString.
`c` : | the character to prepend on the start of the GString.
Returns : | the GString.

### g_string_prepend_unichar ()

    GString*    g_string_prepend_unichar        (GString *string,
                                                 gunichar wc);

Converts a Unicode character into UTF-8, and prepends it to the string.

`string` : | a GString.
`wc` : | a Unicode character.
Returns : | `string`.

### g_string_prepend_len ()

    GString*    g_string_prepend_len            (GString *string,
                                                 const gchar *val,
                                                 gssize len);

Prepends `len` bytes of `val` to `string`. Because `len` is provided, `val` may contain embedded nuls and need not be nul-terminated.

`string` : | a GString.
`val` : | bytes to prepend.
`len` : | number of bytes in `val` to prepend.
Returns : | the GString passed in.

### g_string_insert ()

    GString*    g_string_insert                 (GString *string,
                                                 gssize pos,
                                                 const gchar *val);

Inserts a copy of a string into a GString, expanding it if necessary.

`string` : | a GString.
`pos` : | the position to insert the copy of the string.
`val` : | the string to insert.
Returns : | the GString.

### g_string_insert_c ()

    GString*    g_string_insert_c               (GString *string,
                                                 gssize pos,
                                                 gchar c);

Inserts a character into a GString, expanding it if necessary.

`string` : | a GString.
`pos` : | the position to insert the character.
`c` : | the character to insert.
Returns : | the GString.

### g_string_insert_unichar ()

    GString*    g_string_insert_unichar         (GString *string,
                                                 gssize pos,
                                                 gunichar wc);

Converts a Unicode character into UTF-8, and insert it into the string at the given position.

`string` : | a GString
`pos` : | the position at which to insert character, or -1 to append at the end of the string.
`wc` : | a Unicode character
Returns : | `string`

### g_string_insert_len ()

    GString*    g_string_insert_len             (GString *string,
                                                 gssize pos,
                                                 const gchar *val,
                                                 gssize len);

Inserts `len` bytes of `val` into `string` at `pos`. Because `len` is provided, `val` may contain embedded nuls and need not be nul-terminated. If `pos` is -1, bytes are inserted at the end of the string.

`string` : | a GString.
`pos` : | position in `string` where insertion should happen, or -1 for at the end.
`val` : | bytes to insert.
`len` : | number of bytes of `val` to insert.
Returns : | the GString.

### g_string_erase ()

    GString*    g_string_erase                  (GString *string,
                                                 gssize pos,
                                                 gssize len);

Removes `len` characters from a GString, starting at position `pos`. The rest of the GString is shifted down to fill the gap.

`string` : | a GString.
`pos` : | the position of the characters to remove.
`len` : | the number of characters to remove, or -1 to remove all following characters.
Returns : | the GString.

### g_string_truncate ()

    GString*    g_string_truncate               (GString *string,
                                                 gsize len);

Cuts off the end of the GString, leaving the first `len` characters.

`string` : | a GString.
`len` : | the new size of the GString.
Returns : | the GString.

### g_string_set_size ()

    GString*    g_string_set_size               (GString *string,
                                                 gsize len);

Sets the length of a GString. If the length is less than the current length, the string will be truncated. If the length is greater than the current length, the contents of the newly added area are undefined. (However, as always, string->str[string->len] will be a nul byte.)

`string` : | a GString
`len` : | the new length
Returns : | `string`

### g_string_free ()

    gchar*      g_string_free                   (GString *string,
                                                 gboolean free_segment);

Frees the memory allocated for the GString. If `free_segment` is `TRUE` it also frees the character data.

`string` : | a GString.
`free_segment` : | if `TRUE` the actual character data is freed as well.
Returns : |

### g_string_up ()

    GString*    g_string_up                     (GString *string);

Warning
`g_string_up` is deprecated and should not be used in newly-written code.

Converts a GString to upper case.

`string` : | a GString.
Returns : | the GString.

### g_string_down ()

    GString*    g_string_down                   (GString *string);

Warning
`g_string_down` is deprecated and should not be used in newly-written code.

Converts a GString to lower case.

`string` : | a GString.
Returns : | the GString.

### g_string_hash ()

    guint       g_string_hash                   (const GString *str);

Creates a hash code for `str`; for use with GHashTable.

`str` : | a string to hash.
Returns : | hash code for `str`.

### g_string_equal ()

    gboolean    g_string_equal                  (const GString *v,
                                                 const GString *v2);

Compares two strings for equality, returning `TRUE` if they are equal. For use with GHashTable.

`v` : | a GString.
`v2` : | another GString.
Returns : | `TRUE` if they strings are the same length and contain the same bytes.

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