StringIO

Pseudo I/O on String object, with interface corresponding to IO.

Commonly used to simulate $stdio or $stderr

Examples¶ ↑

require 'stringio'

# Writing stream emulation
io = StringIO.new
io.puts "Hello World"
io.string #=> "Hello World\n"

# Reading stream emulation
io = StringIO.new "first\nsecond\nlast\n"
io.getc #=> "f"
io.gets #=> "irst\n"
io.read #=> "second\nlast\n"

Constants

VERSION

Public Class Methods

new(string=""[, mode]) click to toggle source

Creates new StringIO instance from with string and mode.

 
               static VALUE
strio_initialize(int argc, VALUE *argv, VALUE self)
{
    struct StringIO *ptr = check_strio(self);

    if (!ptr) {
        DATA_PTR(self) = ptr = strio_alloc();
    }
    rb_call_super(0, 0);
    return strio_init(argc, argv, ptr, self);
}

open(string=""[, mode]) {|strio| ...} click to toggle source

Equivalent to ::new except that when it is called with a block, it yields with the new instance and closes it, and returns the result which returned from the block.

 
               static VALUE
strio_s_open(int argc, VALUE *argv, VALUE klass)
{
    VALUE obj = rb_class_new_instance_kw(argc, argv, klass, RB_PASS_CALLED_KEYWORDS);
    if (!rb_block_given_p()) return obj;
    return rb_ensure(rb_yield, obj, strio_finalize, obj);
}

Public Instance Methods

binmode → stringio click to toggle source

Puts stream into binary mode. See IO#binmode.

 
               static VALUE
strio_binmode(VALUE self)
{
    struct StringIO *ptr = StringIO(self);
    rb_encoding *enc = rb_ascii8bit_encoding();

    ptr->enc = enc;
    if (WRITABLE(self)) {
        rb_enc_associate(ptr->string, enc);
    }
    return self;
}

close → nil click to toggle source

Closes a StringIO. The stream is unavailable for any further data operations; an IOError is raised if such an attempt is made.

 
               static VALUE
strio_close(VALUE self)
{
    StringIO(self);
    RBASIC(self)->flags &= ~STRIO_READWRITE;
    return Qnil;
}

close_read → nil click to toggle source

Closes the read end of a StringIO. Will raise an IOError if the receiver is not readable.

 
               static VALUE
strio_close_read(VALUE self)
{
    struct StringIO *ptr = StringIO(self);
    if (!(ptr->flags & FMODE_READABLE)) {
        rb_raise(rb_eIOError, "closing non-duplex IO for reading");
    }
    RBASIC(self)->flags &= ~STRIO_READABLE;
    return Qnil;
}

close_write → nil click to toggle source

Closes the write end of a StringIO. Will raise an IOError if the receiver is not writeable.

 
               static VALUE
strio_close_write(VALUE self)
{
    struct StringIO *ptr = StringIO(self);
    if (!(ptr->flags & FMODE_WRITABLE)) {
        rb_raise(rb_eIOError, "closing non-duplex IO for writing");
    }
    RBASIC(self)->flags &= ~STRIO_WRITABLE;
    return Qnil;
}

closed? → true or false click to toggle source

Returns true if the stream is completely closed, false otherwise.

 
               static VALUE
strio_closed(VALUE self)
{
    StringIO(self);
    if (!CLOSED(self)) return Qfalse;
    return Qtrue;
}

closed_read? → true or false click to toggle source

Returns true if the stream is not readable, false otherwise.

 
               static VALUE
strio_closed_read(VALUE self)
{
    StringIO(self);
    if (READABLE(self)) return Qfalse;
    return Qtrue;
}

closed_write? → true or false click to toggle source

Returns true if the stream is not writable, false otherwise.

 
               static VALUE
strio_closed_write(VALUE self)
{
    StringIO(self);
    if (WRITABLE(self)) return Qfalse;
    return Qtrue;
}

each(sep=$/, chomp: false) {|line| block } → strio click to toggle source

each(limit, chomp: false) {|line| block } → strio

each(sep, limit, chomp: false) {|line| block } → strio

each(...) → anEnumerator

each_line(sep=$/, chomp: false) {|line| block } → strio

each_line(limit, chomp: false) {|line| block } → strio

each_line(sep, limit, chomp: false) {|line| block } → strio

each_line(...) → anEnumerator

See IO#each.

 
               static VALUE
strio_each(int argc, VALUE *argv, VALUE self)
{
    VALUE line;
    struct getline_arg arg;

    StringIO(self);
    RETURN_ENUMERATOR(self, argc, argv);

    if (prepare_getline_args(&arg, argc, argv)->limit == 0) {
        rb_raise(rb_eArgError, "invalid limit: 0 for each_line");
    }

    while (!NIL_P(line = strio_getline(&arg, readable(self)))) {
        rb_yield(line);
    }
    return self;
}

each_byte {|byte| block } → strio click to toggle source

each_byte → anEnumerator

See IO#each_byte.

 
               static VALUE
strio_each_byte(VALUE self)
{
    struct StringIO *ptr;

    RETURN_ENUMERATOR(self, 0, 0);

    while ((ptr = strio_to_read(self)) != NULL) {
        char c = RSTRING_PTR(ptr->string)[ptr->pos++];
        rb_yield(CHR2FIX(c));
    }
    return self;
}

each_char {|char| block } → strio click to toggle source

each_char → anEnumerator

See IO#each_char.

 
               static VALUE
strio_each_char(VALUE self)
{
    VALUE c;

    RETURN_ENUMERATOR(self, 0, 0);

    while (!NIL_P(c = strio_getc(self))) {
        rb_yield(c);
    }
    return self;
}

each_codepoint {|c| block } → strio click to toggle source

each_codepoint → anEnumerator

See IO#each_codepoint.

 
               static VALUE
strio_each_codepoint(VALUE self)
{
    struct StringIO *ptr;
    rb_encoding *enc;
    unsigned int c;
    int n;

    RETURN_ENUMERATOR(self, 0, 0);

    ptr = readable(self);
    enc = get_enc(ptr);
    while ((ptr = strio_to_read(self)) != NULL) {
        c = rb_enc_codepoint_len(RSTRING_PTR(ptr->string)+ptr->pos,
                                 RSTRING_END(ptr->string), &n, enc);
        ptr->pos += n;
        rb_yield(UINT2NUM(c));
    }
    return self;
}

each_line(sep=$/, chomp: false) {|line| block } → strio click to toggle source

each_line(limit, chomp: false) {|line| block } → strio

each_line(sep, limit, chomp: false) {|line| block } → strio

each_line(...) → anEnumerator

See IO#each.

 
               static VALUE
strio_each(int argc, VALUE *argv, VALUE self)
{
    VALUE line;
    struct getline_arg arg;

    StringIO(self);
    RETURN_ENUMERATOR(self, argc, argv);

    if (prepare_getline_args(&arg, argc, argv)->limit == 0) {
        rb_raise(rb_eArgError, "invalid limit: 0 for each_line");
    }

    while (!NIL_P(line = strio_getline(&arg, readable(self)))) {
        rb_yield(line);
    }
    return self;
}

eof → true or false click to toggle source

eof? → true or false

Returns true if the stream is at the end of the data (underlying string). The stream must be opened for reading or an IOError will be raised.

 
               static VALUE
strio_eof(VALUE self)
{
    if (strio_to_read(self)) return Qfalse;
    return Qtrue;
}

eof? → true or false click to toggle source

Returns true if the stream is at the end of the data (underlying string). The stream must be opened for reading or an IOError will be raised.

 
               static VALUE
strio_eof(VALUE self)
{
    if (strio_to_read(self)) return Qfalse;
    return Qtrue;
}

external_encoding => encoding click to toggle source

Returns the Encoding object that represents the encoding of the file. If the stream is write mode and no encoding is specified, returns nil.

 
               static VALUE
strio_external_encoding(VALUE self)
{
    struct StringIO *ptr = StringIO(self);
    return rb_enc_from_encoding(get_enc(ptr));
}

fcntl(*args) click to toggle source

Raises NotImplementedError.

 
               static VALUE
strio_unimpl(int argc, VALUE *argv, VALUE self)
{
    StringIO(self);
    rb_notimplement();

    UNREACHABLE;
}

fileno() click to toggle source

Returns nil. Just for compatibility to IO.

 
               static VALUE
strio_nil(VALUE self)
{
    StringIO(self);
    return Qnil;
}

flush() click to toggle source

Returns an object itself. Just for compatibility to IO.

 
               static VALUE
strio_self(VALUE self)
{
    StringIO(self);
    return self;
}

fsync() click to toggle source

Returns 0. Just for compatibility to IO.

 
               static VALUE
strio_0(VALUE self)
{
    StringIO(self);
    return INT2FIX(0);
}

getbyte → fixnum or nil click to toggle source

See IO#getbyte.

 
               static VALUE
strio_getbyte(VALUE self)
{
    struct StringIO *ptr = readable(self);
    int c;
    if (ptr->pos >= RSTRING_LEN(ptr->string)) {
        return Qnil;
    }
    c = RSTRING_PTR(ptr->string)[ptr->pos++];
    return CHR2FIX(c);
}

getc → string or nil click to toggle source

See IO#getc.

 
               static VALUE
strio_getc(VALUE self)
{
    struct StringIO *ptr = readable(self);
    rb_encoding *enc = get_enc(ptr);
    VALUE str = ptr->string;
    long pos = ptr->pos;
    int len;
    char *p;

    if (pos >= RSTRING_LEN(str)) {
        return Qnil;
    }
    p = RSTRING_PTR(str)+pos;
    len = rb_enc_mbclen(p, RSTRING_END(str), enc);
    ptr->pos += len;
    return enc_subseq(str, pos, len, enc);
}

gets(sep=$/, chomp: false) → string or nil click to toggle source

gets(limit, chomp: false) → string or nil

gets(sep, limit, chomp: false) → string or nil

See IO#gets.

 
               static VALUE
strio_gets(int argc, VALUE *argv, VALUE self)
{
    struct getline_arg arg;
    VALUE str;

    if (prepare_getline_args(&arg, argc, argv)->limit == 0) {
        struct StringIO *ptr = readable(self);
        return rb_enc_str_new(0, 0, get_enc(ptr));
    }

    str = strio_getline(&arg, readable(self));
    rb_lastline_set(str);
    return str;
}

internal_encoding => encoding click to toggle source

Returns the Encoding of the internal string if conversion is specified. Otherwise returns nil.

 
               static VALUE
strio_internal_encoding(VALUE self)
{
    return Qnil;
}

isatty() click to toggle source

Returns false. Just for compatibility to IO.

 
               static VALUE
strio_false(VALUE self)
{
    StringIO(self);
    return Qfalse;
}

length → integer click to toggle source

Returns the size of the buffer string.

 
               static VALUE
strio_size(VALUE self)
{
    VALUE string = StringIO(self)->string;
    if (NIL_P(string)) {
        rb_raise(rb_eIOError, "not opened");
    }
    return ULONG2NUM(RSTRING_LEN(string));
}

lineno → integer click to toggle source

Returns the current line number. The stream must be opened for reading. lineno counts the number of times gets is called, rather than the number of newlines encountered. The two values will differ if gets is called with a separator other than newline. See also the $. variable.

 
               static VALUE
strio_get_lineno(VALUE self)
{
    return LONG2NUM(StringIO(self)->lineno);
}

lineno = integer → integer click to toggle source

Manually sets the current line number to the given value. $. is updated only on the next read.

 
               static VALUE
strio_set_lineno(VALUE self, VALUE lineno)
{
    StringIO(self)->lineno = NUM2LONG(lineno);
    return lineno;
}

pid() click to toggle source

Returns nil. Just for compatibility to IO.

 
               static VALUE
strio_nil(VALUE self)
{
    StringIO(self);
    return Qnil;
}

pos → integer click to toggle source

tell → integer

Returns the current offset (in bytes).

 
               static VALUE
strio_get_pos(VALUE self)
{
    return LONG2NUM(StringIO(self)->pos);
}

pos = integer → integer click to toggle source

Seeks to the given position (in bytes).

 
               static VALUE
strio_set_pos(VALUE self, VALUE pos)
{
    struct StringIO *ptr = StringIO(self);
    long p = NUM2LONG(pos);
    if (p < 0) {
        error_inval(0);
    }
    ptr->pos = p;
    return pos;
}

putc(obj) → obj click to toggle source

See IO#putc.

 
               static VALUE
strio_putc(VALUE self, VALUE ch)
{
    struct StringIO *ptr = writable(self);
    VALUE str;

    check_modifiable(ptr);
    if (RB_TYPE_P(ch, T_STRING)) {
        str = rb_str_substr(ch, 0, 1);
    }
    else {
        char c = NUM2CHR(ch);
        str = rb_str_new(&c, 1);
    }
    strio_write(self, str);
    return ch;
}

read([length [, outbuf]]) → string, outbuf, or nil click to toggle source

See IO#read.

 
               static VALUE
strio_read(int argc, VALUE *argv, VALUE self)
{
    struct StringIO *ptr = readable(self);
    VALUE str = Qnil;
    long len;
    int binary = 0;

    switch (argc) {
      case 2:
        str = argv[1];
        if (!NIL_P(str)) {
            StringValue(str);
            rb_str_modify(str);
        }
        /* fall through */
      case 1:
        if (!NIL_P(argv[0])) {
            len = NUM2LONG(argv[0]);
            if (len < 0) {
                rb_raise(rb_eArgError, "negative length %ld given", len);
            }
            if (len > 0 && ptr->pos >= RSTRING_LEN(ptr->string)) {
                if (!NIL_P(str)) rb_str_resize(str, 0);
                return Qnil;
            }
            binary = 1;
            break;
        }
        /* fall through */
      case 0:
        len = RSTRING_LEN(ptr->string);
        if (len <= ptr->pos) {
            rb_encoding *enc = get_enc(ptr);
            if (NIL_P(str)) {
                str = rb_str_new(0, 0);
            }
            else {
                rb_str_resize(str, 0);
            }
            rb_enc_associate(str, enc);
            return str;
        }
        else {
            len -= ptr->pos;
        }
        break;
      default:
        rb_error_arity(argc, 0, 2);
    }
    if (NIL_P(str)) {
        rb_encoding *enc = binary ? rb_ascii8bit_encoding() : get_enc(ptr);
        str = strio_substr(ptr, ptr->pos, len, enc);
    }
    else {
        long rest = RSTRING_LEN(ptr->string) - ptr->pos;
        if (len > rest) len = rest;
        rb_str_resize(str, len);
        MEMCPY(RSTRING_PTR(str), RSTRING_PTR(ptr->string) + ptr->pos, char, len);
        if (binary)
            rb_enc_associate(str, rb_ascii8bit_encoding());
        else
            rb_enc_copy(str, ptr->string);
    }
    ptr->pos += RSTRING_LEN(str);
    return str;
}

readlines(sep=$/, chomp: false) → array click to toggle source

readlines(limit, chomp: false) → array

readlines(sep, limit, chomp: false) → array

See IO#readlines.

 
               static VALUE
strio_readlines(int argc, VALUE *argv, VALUE self)
{
    VALUE ary, line;
    struct getline_arg arg;

    StringIO(self);
    ary = rb_ary_new();
    if (prepare_getline_args(&arg, argc, argv)->limit == 0) {
        rb_raise(rb_eArgError, "invalid limit: 0 for readlines");
    }

    while (!NIL_P(line = strio_getline(&arg, readable(self)))) {
        rb_ary_push(ary, line);
    }
    return ary;
}

reopen(other_StrIO) → strio click to toggle source

reopen(string, mode) → strio

Reinitializes the stream with the given other_StrIO or string and mode (see StringIO#new).

 
               static VALUE
strio_reopen(int argc, VALUE *argv, VALUE self)
{
    rb_io_taint_check(self);
    if (argc == 1 && !RB_TYPE_P(*argv, T_STRING)) {
        return strio_copy(self, *argv);
    }
    return strio_init(argc, argv, StringIO(self), self);
}

rewind → 0 click to toggle source

Positions the stream to the beginning of input, resetting lineno to zero.

 
               static VALUE
strio_rewind(VALUE self)
{
    struct StringIO *ptr = StringIO(self);
    ptr->pos = 0;
    ptr->lineno = 0;
    return INT2FIX(0);
}

seek(amount, whence=SEEK_SET) → 0 click to toggle source

Seeks to a given offset amount in the stream according to the value of whence (see IO#seek).

 
               static VALUE
strio_seek(int argc, VALUE *argv, VALUE self)
{
    VALUE whence;
    struct StringIO *ptr = StringIO(self);
    long amount, offset;

    rb_scan_args(argc, argv, "11", NULL, &whence);
    amount = NUM2LONG(argv[0]);
    if (CLOSED(self)) {
        rb_raise(rb_eIOError, "closed stream");
    }
    switch (NIL_P(whence) ? 0 : NUM2LONG(whence)) {
      case 0:
        offset = 0;
        break;
      case 1:
        offset = ptr->pos;
        break;
      case 2:
        offset = RSTRING_LEN(ptr->string);
        break;
      default:
        error_inval("invalid whence");
    }
    if (amount > LONG_MAX - offset || amount + offset < 0) {
        error_inval(0);
    }
    ptr->pos = amount + offset;
    return INT2FIX(0);
}

set_encoding(ext_enc, [int_enc[, opt]]) => strio click to toggle source

Specify the encoding of the StringIO as ext_enc. Use the default external encoding if ext_enc is nil. 2nd argument int_enc and optional hash opt argument are ignored; they are for API compatibility to IO.

 
               static VALUE
strio_set_encoding(int argc, VALUE *argv, VALUE self)
{
    rb_encoding* enc;
    struct StringIO *ptr = StringIO(self);
    VALUE ext_enc, int_enc, opt;

    argc = rb_scan_args(argc, argv, "11:", &ext_enc, &int_enc, &opt);

    if (NIL_P(ext_enc)) {
        enc = rb_default_external_encoding();
    }
    else {
        enc = rb_to_encoding(ext_enc);
    }
    ptr->enc = enc;
    if (WRITABLE(self)) {
        rb_enc_associate(ptr->string, enc);
    }

    return self;
}

set_encoding_by_bom() click to toggle source

 
               static VALUE
strio_set_encoding_by_bom(VALUE self)
{
    struct StringIO *ptr = StringIO(self);

    if (!set_encoding_by_bom(ptr)) return Qnil;
    return rb_enc_from_encoding(ptr->enc);
}

size → integer click to toggle source

Returns the size of the buffer string.

 
               static VALUE
strio_size(VALUE self)
{
    VALUE string = StringIO(self)->string;
    if (NIL_P(string)) {
        rb_raise(rb_eIOError, "not opened");
    }
    return ULONG2NUM(RSTRING_LEN(string));
}

string → string click to toggle source

Returns underlying String object, the subject of IO.

 
               static VALUE
strio_get_string(VALUE self)
{
    return StringIO(self)->string;
}

string = string → string click to toggle source

Changes underlying String object, the subject of IO.

 
               static VALUE
strio_set_string(VALUE self, VALUE string)
{
    struct StringIO *ptr = StringIO(self);

    rb_io_taint_check(self);
    ptr->flags &= ~FMODE_READWRITE;
    StringValue(string);
    ptr->flags = OBJ_FROZEN(string) ? FMODE_READABLE : FMODE_READWRITE;
    ptr->pos = 0;
    ptr->lineno = 0;
    return ptr->string = string;
}

sync → true click to toggle source

Returns true always.

 
               static VALUE
strio_get_sync(VALUE self)
{
    StringIO(self);
    return Qtrue;
}

sync=(p1) click to toggle source

Returns the argument unchanged. Just for compatibility to IO.

 
               static VALUE
strio_first(VALUE self, VALUE arg)
{
    StringIO(self);
    return arg;
}

pos → integer click to toggle source

tell → integer

Returns the current offset (in bytes).

 
               static VALUE
strio_get_pos(VALUE self)
{
    return LONG2NUM(StringIO(self)->pos);
}

truncate(integer) → 0 click to toggle source

Truncates the buffer string to at most integer bytes. The stream must be opened for writing.

 
               static VALUE
strio_truncate(VALUE self, VALUE len)
{
    VALUE string = writable(self)->string;
    long l = NUM2LONG(len);
    long plen = RSTRING_LEN(string);
    if (l < 0) {
        error_inval("negative length");
    }
    rb_str_resize(string, l);
    if (plen < l) {
        MEMZERO(RSTRING_PTR(string) + plen, char, l - plen);
    }
    return len;
}

tty?() click to toggle source

Returns false. Just for compatibility to IO.

 
               static VALUE
strio_false(VALUE self)
{
    StringIO(self);
    return Qfalse;
}

ungetbyte(fixnum) → nil click to toggle source

See IO#ungetbyte

 
               static VALUE
strio_ungetbyte(VALUE self, VALUE c)
{
    struct StringIO *ptr = readable(self);

    check_modifiable(ptr);
    if (NIL_P(c)) return Qnil;
    if (RB_INTEGER_TYPE_P(c)) {
        /* rb_int_and() not visible from exts */
        VALUE v = rb_funcall(c, '&', 1, INT2FIX(0xff));
        const char cc = NUM2INT(v) & 0xFF;
        strio_unget_bytes(ptr, &cc, 1);
    }
    else {
        long cl;
        SafeStringValue(c);
        cl = RSTRING_LEN(c);
        if (cl > 0) {
            strio_unget_bytes(ptr, RSTRING_PTR(c), cl);
            RB_GC_GUARD(c);
        }
    }
    return Qnil;
}

ungetc(string) → nil click to toggle source

Pushes back one character (passed as a parameter) such that a subsequent buffered read will return it. There is no limitation for multiple pushbacks including pushing back behind the beginning of the buffer string.

 
               static VALUE
strio_ungetc(VALUE self, VALUE c)
{
    struct StringIO *ptr = readable(self);
    rb_encoding *enc, *enc2;

    check_modifiable(ptr);
    if (NIL_P(c)) return Qnil;
    if (RB_INTEGER_TYPE_P(c)) {
        int len, cc = NUM2INT(c);
        char buf[16];

        enc = rb_enc_get(ptr->string);
        len = rb_enc_codelen(cc, enc);
        if (len <= 0) rb_enc_uint_chr(cc, enc);
        rb_enc_mbcput(cc, buf, enc);
        return strio_unget_bytes(ptr, buf, len);
    }
    else {
        SafeStringValue(c);
        enc = rb_enc_get(ptr->string);
        enc2 = rb_enc_get(c);
        if (enc != enc2 && enc != rb_ascii8bit_encoding()) {
            c = rb_str_conv_enc(c, enc2, enc);
        }
        strio_unget_bytes(ptr, RSTRING_PTR(c), RSTRING_LEN(c));
        RB_GC_GUARD(c);
        return Qnil;
    }
}

write(string, ...) → integer click to toggle source

syswrite(string) → integer

Appends the given string to the underlying buffer string. The stream must be opened for writing. If the argument is not a string, it will be converted to a string using to_s. Returns the number of bytes written. See IO#write.

 
               static VALUE
strio_write_m(int argc, VALUE *argv, VALUE self)
{
    long len = 0;
    while (argc-- > 0) {
        /* StringIO can't exceed long limit */
        len += strio_write(self, *argv++);
    }
    return LONG2NUM(len);
}

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