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-rw-r--r--std/mem.zig88
1 files changed, 86 insertions, 2 deletions
diff --git a/std/mem.zig b/std/mem.zig
index 8a59d6251b..cc3161cddd 100644
--- a/std/mem.zig
+++ b/std/mem.zig
@@ -11,6 +11,8 @@ pub const Allocator = struct {
/// Allocate byte_count bytes and return them in a slice, with the
/// slice's pointer aligned at least to alignment bytes.
/// The returned newly allocated memory is undefined.
+ /// `alignment` is guaranteed to be >= 1
+ /// `alignment` is guaranteed to be a power of 2
allocFn: fn (self: &Allocator, byte_count: usize, alignment: u29) Error![]u8,
/// If `new_byte_count > old_mem.len`:
@@ -18,10 +20,12 @@ pub const Allocator = struct {
/// * alignment >= alignment of old_mem.ptr
///
/// If `new_byte_count <= old_mem.len`:
- /// * this function must return successfully.
+ /// * this function must return successfully.
/// * alignment <= alignment of old_mem.ptr
///
/// The returned newly allocated memory is undefined.
+ /// `alignment` is guaranteed to be >= 1
+ /// `alignment` is guaranteed to be a power of 2
reallocFn: fn (self: &Allocator, old_mem: []u8, new_byte_count: usize, alignment: u29) Error![]u8,
/// Guaranteed: `old_mem.len` is the same as what was returned from `allocFn` or `reallocFn`
@@ -170,6 +174,20 @@ pub fn dupe(allocator: &Allocator, comptime T: type, m: []const T) ![]T {
return new_buf;
}
+/// Remove values from the beginning of a slice.
+pub fn trimLeft(comptime T: type, slice: []const T, values_to_strip: []const T) []const T {
+ var begin: usize = 0;
+ while (begin < slice.len and indexOfScalar(T, values_to_strip, slice[begin]) != null) : (begin += 1) {}
+ return slice[begin..];
+}
+
+/// Remove values from the end of a slice.
+pub fn trimRight(comptime T: type, slice: []const T, values_to_strip: []const T) []const T {
+ var end: usize = slice.len;
+ while (end > 0 and indexOfScalar(T, values_to_strip, slice[end - 1]) != null) : (end -= 1) {}
+ return slice[0..end];
+}
+
/// Remove values from the beginning and end of a slice.
pub fn trim(comptime T: type, slice: []const T, values_to_strip: []const T) []const T {
var begin: usize = 0;
@@ -180,6 +198,8 @@ pub fn trim(comptime T: type, slice: []const T, values_to_strip: []const T) []co
}
test "mem.trim" {
+ assert(eql(u8, trimLeft(u8, " foo\n ", " \n"), "foo\n "));
+ assert(eql(u8, trimRight(u8, " foo\n ", " \n"), " foo"));
assert(eql(u8, trim(u8, " foo\n ", " \n"), "foo"));
assert(eql(u8, trim(u8, "foo", " \n"), "foo"));
}
@@ -189,6 +209,17 @@ pub fn indexOfScalar(comptime T: type, slice: []const T, value: T) ?usize {
return indexOfScalarPos(T, slice, 0, value);
}
+/// Linear search for the last index of a scalar value inside a slice.
+pub fn lastIndexOfScalar(comptime T: type, slice: []const T, value: T) ?usize {
+ var i: usize = slice.len;
+ while (i != 0) {
+ i -= 1;
+ if (slice[i] == value)
+ return i;
+ }
+ return null;
+}
+
pub fn indexOfScalarPos(comptime T: type, slice: []const T, start_index: usize, value: T) ?usize {
var i: usize = start_index;
while (i < slice.len) : (i += 1) {
@@ -202,6 +233,18 @@ pub fn indexOfAny(comptime T: type, slice: []const T, values: []const T) ?usize
return indexOfAnyPos(T, slice, 0, values);
}
+pub fn lastIndexOfAny(comptime T: type, slice: []const T, values: []const T) ?usize {
+ var i: usize = slice.len;
+ while (i != 0) {
+ i -= 1;
+ for (values) |value| {
+ if (slice[i] == value)
+ return i;
+ }
+ }
+ return null;
+}
+
pub fn indexOfAnyPos(comptime T: type, slice: []const T, start_index: usize, values: []const T) ?usize {
var i: usize = start_index;
while (i < slice.len) : (i += 1) {
@@ -217,6 +260,22 @@ pub fn indexOf(comptime T: type, haystack: []const T, needle: []const T) ?usize
return indexOfPos(T, haystack, 0, needle);
}
+/// Find the index in a slice of a sub-slice, searching from the end backwards.
+/// To start looking at a different index, slice the haystack first.
+/// TODO is there even a better algorithm for this?
+pub fn lastIndexOf(comptime T: type, haystack: []const T, needle: []const T) ?usize {
+ if (needle.len > haystack.len)
+ return null;
+
+ var i: usize = haystack.len - needle.len;
+ while (true) : (i -= 1) {
+ if (mem.eql(T, haystack[i..i+needle.len], needle))
+ return i;
+ if (i == 0)
+ return null;
+ }
+}
+
// TODO boyer-moore algorithm
pub fn indexOfPos(comptime T: type, haystack: []const T, start_index: usize, needle: []const T) ?usize {
if (needle.len > haystack.len)
@@ -233,9 +292,19 @@ pub fn indexOfPos(comptime T: type, haystack: []const T, start_index: usize, nee
test "mem.indexOf" {
assert(??indexOf(u8, "one two three four", "four") == 14);
+ assert(??lastIndexOf(u8, "one two three two four", "two") == 14);
assert(indexOf(u8, "one two three four", "gour") == null);
+ assert(lastIndexOf(u8, "one two three four", "gour") == null);
assert(??indexOf(u8, "foo", "foo") == 0);
+ assert(??lastIndexOf(u8, "foo", "foo") == 0);
assert(indexOf(u8, "foo", "fool") == null);
+ assert(lastIndexOf(u8, "foo", "lfoo") == null);
+ assert(lastIndexOf(u8, "foo", "fool") == null);
+
+ assert(??indexOf(u8, "foo foo", "foo") == 0);
+ assert(??lastIndexOf(u8, "foo foo", "foo") == 4);
+ assert(??lastIndexOfAny(u8, "boo, cat", "abo") == 6);
+ assert(??lastIndexOfScalar(u8, "boo", 'o') == 2);
}
/// Reads an integer from memory with size equal to bytes.len.
@@ -355,9 +424,24 @@ pub fn startsWith(comptime T: type, haystack: []const T, needle: []const T) bool
return if (needle.len > haystack.len) false else eql(T, haystack[0 .. needle.len], needle);
}
+test "mem.startsWith" {
+ assert(startsWith(u8, "Bob", "Bo"));
+ assert(!startsWith(u8, "Needle in haystack", "haystack"));
+}
+
+pub fn endsWith(comptime T: type, haystack: []const T, needle: []const T) bool {
+ return if (needle.len > haystack.len) false else eql(T, haystack[haystack.len - needle.len ..], needle);
+}
+
+
+test "mem.endsWith" {
+ assert(endsWith(u8, "Needle in haystack", "haystack"));
+ assert(!endsWith(u8, "Bob", "Bo"));
+}
+
pub const SplitIterator = struct {
buffer: []const u8,
- split_bytes: []const u8,
+ split_bytes: []const u8,
index: usize,
pub fn next(self: &SplitIterator) ?[]const u8 {
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