Struct collections::string::String
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[src]
pub struct String {
// some fields omitted
}A growable string stored as a UTF-8 encoded buffer.
Methods
impl String
fn new() -> String
Creates a new string buffer initialized with the empty string.
Examples
fn main() { let mut s = String::new(); }let mut s = String::new();
fn with_capacity(capacity: usize) -> String
Creates a new string buffer with the given capacity.
The string will be able to hold exactly capacity bytes without
reallocating. If capacity is 0, the string will not allocate.
Examples
fn main() { let mut s = String::with_capacity(10); }let mut s = String::with_capacity(10);
fn from_utf8(vec: Vec<u8>) -> Result<String, FromUtf8Error>
Returns the vector as a string buffer, if possible, taking care not to copy it.
Failure
If the given vector is not valid UTF-8, then the original vector and the corresponding error is returned.
Examples
fn main() { let hello_vec = vec![104, 101, 108, 108, 111]; let s = String::from_utf8(hello_vec).unwrap(); assert_eq!(s, "hello"); let invalid_vec = vec![240, 144, 128]; let s = String::from_utf8(invalid_vec).err().unwrap(); let err = s.utf8_error(); assert_eq!(s.into_bytes(), [240, 144, 128]); }let hello_vec = vec![104, 101, 108, 108, 111]; let s = String::from_utf8(hello_vec).unwrap(); assert_eq!(s, "hello"); let invalid_vec = vec![240, 144, 128]; let s = String::from_utf8(invalid_vec).err().unwrap(); let err = s.utf8_error(); assert_eq!(s.into_bytes(), [240, 144, 128]);
fn from_utf8_lossy<'a>(v: &'a [u8]) -> Cow<'a, str>
Converts a vector of bytes to a new UTF-8 string. Any invalid UTF-8 sequences are replaced with U+FFFD REPLACEMENT CHARACTER.
Examples
fn main() { let input = b"Hello \xF0\x90\x80World"; let output = String::from_utf8_lossy(input); assert_eq!(output, "Hello \u{FFFD}World"); }let input = b"Hello \xF0\x90\x80World"; let output = String::from_utf8_lossy(input); assert_eq!(output, "Hello \u{FFFD}World");
fn from_utf16(v: &[u16]) -> Result<String, FromUtf16Error>
Decode a UTF-16 encoded vector v into a String, returning None
if v contains any invalid data.
Examples
fn main() { // 𝄞music let mut v = &mut [0xD834, 0xDD1E, 0x006d, 0x0075, 0x0073, 0x0069, 0x0063]; assert_eq!(String::from_utf16(v).unwrap(), "𝄞music".to_string()); // 𝄞mu<invalid>ic v[4] = 0xD800; assert!(String::from_utf16(v).is_err()); }// 𝄞music let mut v = &mut [0xD834, 0xDD1E, 0x006d, 0x0075, 0x0073, 0x0069, 0x0063]; assert_eq!(String::from_utf16(v).unwrap(), "𝄞music".to_string()); // 𝄞mu<invalid>ic v[4] = 0xD800; assert!(String::from_utf16(v).is_err());
fn from_utf16_lossy(v: &[u16]) -> String
Decode a UTF-16 encoded vector v into a string, replacing
invalid data with the replacement character (U+FFFD).
Examples
fn main() { // 𝄞mus<invalid>ic<invalid> let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, 0x0073, 0xDD1E, 0x0069, 0x0063, 0xD834]; assert_eq!(String::from_utf16_lossy(v), "𝄞mus\u{FFFD}ic\u{FFFD}".to_string()); }// 𝄞mus<invalid>ic<invalid> let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, 0x0073, 0xDD1E, 0x0069, 0x0063, 0xD834]; assert_eq!(String::from_utf16_lossy(v), "𝄞mus\u{FFFD}ic\u{FFFD}".to_string());
unsafe fn from_raw_parts(buf: *mut u8, length: usize, capacity: usize) -> String
Creates a new String from a length, capacity, and pointer.
Unsafety
This is very unsafe because:
- We call
Vec::from_raw_partsto get aVec<u8>. Therefore, this function inherits all of its unsafety, see its documentation for the invariants it expects, they also apply to this function. - We assume that the
Veccontains valid UTF-8.
unsafe fn from_utf8_unchecked(bytes: Vec<u8>) -> String
Converts a vector of bytes to a new String without checking if
it contains valid UTF-8. This is unsafe because it assumes that
the UTF-8-ness of the vector has already been validated.
fn into_bytes(self) -> Vec<u8>
Returns the underlying byte buffer, encoded as UTF-8.
Examples
fn main() { let s = String::from("hello"); let bytes = s.into_bytes(); assert_eq!(bytes, [104, 101, 108, 108, 111]); }let s = String::from("hello"); let bytes = s.into_bytes(); assert_eq!(bytes, [104, 101, 108, 108, 111]);
fn as_str(&self) -> &str
Extracts a string slice containing the entire string.
fn push_str(&mut self, string: &str)
Pushes the given string onto this string buffer.
Examples
fn main() { let mut s = String::from("foo"); s.push_str("bar"); assert_eq!(s, "foobar"); }let mut s = String::from("foo"); s.push_str("bar"); assert_eq!(s, "foobar");
fn capacity(&self) -> usize
Returns the number of bytes that this string buffer can hold without reallocating.
Examples
fn main() { let s = String::with_capacity(10); assert!(s.capacity() >= 10); }let s = String::with_capacity(10); assert!(s.capacity() >= 10);
fn reserve(&mut self, additional: usize)
Reserves capacity for at least additional more bytes to be inserted
in the given String. The collection may reserve more space to avoid
frequent reallocations.
Panics
Panics if the new capacity overflows usize.
Examples
fn main() { let mut s = String::new(); s.reserve(10); assert!(s.capacity() >= 10); }let mut s = String::new(); s.reserve(10); assert!(s.capacity() >= 10);
fn reserve_exact(&mut self, additional: usize)
Reserves the minimum capacity for exactly additional more bytes to be
inserted in the given String. Does nothing if the capacity is already
sufficient.
Note that the allocator may give the collection more space than it
requests. Therefore capacity can not be relied upon to be precisely
minimal. Prefer reserve if future insertions are expected.
Panics
Panics if the new capacity overflows usize.
Examples
fn main() { let mut s = String::new(); s.reserve_exact(10); assert!(s.capacity() >= 10); }let mut s = String::new(); s.reserve_exact(10); assert!(s.capacity() >= 10);
fn shrink_to_fit(&mut self)
Shrinks the capacity of this string buffer to match its length.
Examples
fn main() { let mut s = String::from("foo"); s.reserve(100); assert!(s.capacity() >= 100); s.shrink_to_fit(); assert_eq!(s.capacity(), 3); }let mut s = String::from("foo"); s.reserve(100); assert!(s.capacity() >= 100); s.shrink_to_fit(); assert_eq!(s.capacity(), 3);
fn push(&mut self, ch: char)
Adds the given character to the end of the string.
Examples
fn main() { let mut s = String::from("abc"); s.push('1'); s.push('2'); s.push('3'); assert_eq!(s, "abc123"); }let mut s = String::from("abc"); s.push('1'); s.push('2'); s.push('3'); assert_eq!(s, "abc123");
fn as_bytes(&self) -> &[u8]
Works with the underlying buffer as a byte slice.
Examples
fn main() { let s = String::from("hello"); assert_eq!(s.as_bytes(), [104, 101, 108, 108, 111]); }let s = String::from("hello"); assert_eq!(s.as_bytes(), [104, 101, 108, 108, 111]);
fn truncate(&mut self, new_len: usize)
Shortens a string to the specified length.
Panics
Panics if new_len > current length,
or if new_len is not a character boundary.
Examples
fn main() { let mut s = String::from("hello"); s.truncate(2); assert_eq!(s, "he"); }let mut s = String::from("hello"); s.truncate(2); assert_eq!(s, "he");
fn pop(&mut self) -> Option<char>
Removes the last character from the string buffer and returns it.
Returns None if this string buffer is empty.
Examples
fn main() { let mut s = String::from("foo"); assert_eq!(s.pop(), Some('o')); assert_eq!(s.pop(), Some('o')); assert_eq!(s.pop(), Some('f')); assert_eq!(s.pop(), None); }let mut s = String::from("foo"); assert_eq!(s.pop(), Some('o')); assert_eq!(s.pop(), Some('o')); assert_eq!(s.pop(), Some('f')); assert_eq!(s.pop(), None);
fn remove(&mut self, idx: usize) -> char
Removes the character from the string buffer at byte position idx and
returns it.
Warning
This is an O(n) operation as it requires copying every element in the buffer.
Panics
If idx does not lie on a character boundary, or if it is out of
bounds, then this function will panic.
Examples
fn main() { let mut s = String::from("foo"); assert_eq!(s.remove(0), 'f'); assert_eq!(s.remove(1), 'o'); assert_eq!(s.remove(0), 'o'); }let mut s = String::from("foo"); assert_eq!(s.remove(0), 'f'); assert_eq!(s.remove(1), 'o'); assert_eq!(s.remove(0), 'o');
fn insert(&mut self, idx: usize, ch: char)
Inserts a character into the string buffer at byte position idx.
Warning
This is an O(n) operation as it requires copying every element in the buffer.
Panics
If idx does not lie on a character boundary or is out of bounds, then
this function will panic.
unsafe fn as_mut_vec(&mut self) -> &mut Vec<u8>
Views the string buffer as a mutable sequence of bytes.
This is unsafe because it does not check to ensure that the resulting string will be valid UTF-8.
Examples
fn main() { let mut s = String::from("hello"); unsafe { let vec = s.as_mut_vec(); assert!(vec == &[104, 101, 108, 108, 111]); vec.reverse(); } assert_eq!(s, "olleh"); }let mut s = String::from("hello"); unsafe { let vec = s.as_mut_vec(); assert!(vec == &[104, 101, 108, 108, 111]); vec.reverse(); } assert_eq!(s, "olleh");
fn len(&self) -> usize
Returns the number of bytes in this string.
Examples
fn main() { let a = "foo".to_string(); assert_eq!(a.len(), 3); }let a = "foo".to_string(); assert_eq!(a.len(), 3);
fn is_empty(&self) -> bool
Returns true if the string contains no bytes
Examples
fn main() { let mut v = String::new(); assert!(v.is_empty()); v.push('a'); assert!(!v.is_empty()); }let mut v = String::new(); assert!(v.is_empty()); v.push('a'); assert!(!v.is_empty());
fn clear(&mut self)
Truncates the string, returning it to 0 length.
Examples
fn main() { let mut s = "foo".to_string(); s.clear(); assert!(s.is_empty()); }let mut s = "foo".to_string(); s.clear(); assert!(s.is_empty());
fn drain<R>(&mut self, range: R) -> Drain where R: RangeArgument<usize>
Create a draining iterator that removes the specified range in the string and yields the removed chars from start to end. The element range is removed even if the iterator is not consumed until the end.
Panics
Panics if the starting point or end point are not on character boundaries, or if they are out of bounds.
Examples
#![feature(drain)] fn main() { let mut s = String::from("α is alpha, β is beta"); let beta_offset = s.find('β').unwrap_or(s.len()); // Remove the range up until the β from the string let t: String = s.drain(..beta_offset).collect(); assert_eq!(t, "α is alpha, "); assert_eq!(s, "β is beta"); // A full range clears the string s.drain(..); assert_eq!(s, ""); }#![feature(drain)] let mut s = String::from("α is alpha, β is beta"); let beta_offset = s.find('β').unwrap_or(s.len()); // Remove the range up until the β from the string let t: String = s.drain(..beta_offset).collect(); assert_eq!(t, "α is alpha, "); assert_eq!(s, "β is beta"); // A full range clears the string s.drain(..); assert_eq!(s, "");
fn into_boxed_str(self) -> Box<str>
Converts the string into Box<str>.
Note that this will drop any excess capacity.
fn into_boxed_slice(self) -> Box<str>
: renamed to into_boxed_str
Converts the string into Box<str>.
Note that this will drop any excess capacity.
Trait Implementations
impl Borrow<str> for String
fn borrow(&self) -> &str
impl FromIterator<char> for String
fn from_iter<I: IntoIterator<Item=char>>(iter: I) -> String
impl<'a> FromIterator<&'a str> for String
fn from_iter<I: IntoIterator<Item=&'a str>>(iter: I) -> String
impl Extend<char> for String
fn extend<I: IntoIterator<Item=char>>(&mut self, iterable: I)
impl<'a> Extend<&'a char> for String
fn extend<I: IntoIterator<Item=&'a char>>(&mut self, iter: I)
impl<'a> Extend<&'a str> for String
fn extend<I: IntoIterator<Item=&'a str>>(&mut self, iterable: I)
impl<'a, 'b> Pattern<'a> for &'b String
A convenience impl that delegates to the impl for &str