1 files changed, 187 insertions, 0 deletions
diff --git a/src/display/display_sink/imp_x86.rs b/src/display/display_sink/imp_x86.rs
new file mode 100644
index 0000000..902ea69
--- /dev/null
+++ b/src/display/display_sink/imp_x86.rs
@@ -0,0 +1,187 @@
+//! `imp_x86` has specialized copies to append short strings to strings. buffer sizing must be
+//! handled by callers, in all cases.
+//!
+//! the structure of all implementations here is, essentially, to take the size of the data to
+//! append and execute a copy for each bit set in that size, from highest to lowest. some bits are
+//! simply never checked if the input is promised to never be that large - if a string to append is
+//! only 0..7 bytes long, it is sufficient to only look at the low three bits to copy all bytes.
+//!
+//! in this way, it is slightly more efficient to right-size which append function is used, if the
+//! maximum size of input strings can be bounded well. if the maximum size of input strings cannot
+//! be bounded, you shouldn't be using these functions.
+
+/// append `data` to `buf`, assuming `data` is less than 8 bytes and that `buf` has enough space
+/// remaining to hold all bytes in `data`.
+///
+/// Safety: callers must ensure that `buf.capacity() - buf.len() >= data.len()`.
+#[inline(always)]
+pub unsafe fn append_string_lt_8_unchecked(buf: &mut alloc::string::String, data: &str) {
+    // Safety: we are appending only valid utf8 strings to `self.buf`, as `s` is known to
+    // be valid utf8
+    let buf = unsafe { buf.as_mut_vec() };
+    let new_bytes = data.as_bytes();
+
+    unsafe {
+        let dest = buf.as_mut_ptr().offset(buf.len() as isize);
+        let src = new_bytes.as_ptr();
+
+        let rem = new_bytes.len() as isize;
+
+        // set_len early because there is no way to avoid the following asm!() writing that
+        // same number of bytes into buf
+        buf.set_len(buf.len() + new_bytes.len());
+
+        core::arch::asm!(
+            "8:",
+            "cmp {rem:e}, 4",
+            "jb 9f",
+            "mov {buf:e}, dword ptr [{src} + {rem} - 4]",
+            "mov dword ptr [{dest} + {rem} - 4], {buf:e}",
+            "sub {rem:e}, 4",
+            "jz 11f",
+            "9:",
+            "cmp {rem:e}, 2",
+            "jb 10f",
+            "mov {buf:x}, word ptr [{src} + {rem} - 2]",
+            "mov word ptr [{dest} + {rem} - 2], {buf:x}",
+            "sub {rem:e}, 2",
+            "jz 11f",
+            "10:",
+            "cmp {rem:e}, 1",
+            "jb 11f",
+            "mov {buf:l}, byte ptr [{src} + {rem} - 1]",
+            "mov byte ptr [{dest} + {rem} - 1], {buf:l}",
+            "11:",
+            src = in(reg) src,
+            dest = in(reg) dest,
+            rem = inout(reg) rem => _,
+            buf = out(reg) _,
+            options(nostack),
+        );
+    }
+}
+
+/// append `data` to `buf`, assuming `data` is less than 16 bytes and that `buf` has enough space
+/// remaining to hold all bytes in `data`.
+///
+/// Safety: callers must ensure that `buf.capacity() - buf.len() >= data.len()`.
+#[inline(always)]
+pub unsafe fn append_string_lt_16_unchecked(buf: &mut alloc::string::String, data: &str) {
+    // Safety: we are appending only valid utf8 strings to `self.buf`, as `s` is known to
+    // be valid utf8
+    let buf = unsafe { buf.as_mut_vec() };
+    let new_bytes = data.as_bytes();
+
+    unsafe {
+        let dest = buf.as_mut_ptr().offset(buf.len() as isize);
+        let src = new_bytes.as_ptr();
+
+        let rem = new_bytes.len() as isize;
+
+        // set_len early because there is no way to avoid the following asm!() writing that
+        // same number of bytes into buf
+        buf.set_len(buf.len() + new_bytes.len());
+
+        core::arch::asm!(
+            "7:",
+            "cmp {rem:e}, 8",
+            "jb 8f",
+            "mov {buf:r}, qword ptr [{src} + {rem} - 8]",
+            "mov qword ptr [{dest} + {rem} - 8], {buf:r}",
+            "sub {rem:e}, 8",
+            "jz 11f",
+            "8:",
+            "cmp {rem:e}, 4",
+            "jb 9f",
+            "mov {buf:e}, dword ptr [{src} + {rem} - 4]",
+            "mov dword ptr [{dest} + {rem} - 4], {buf:e}",
+            "sub {rem:e}, 4",
+            "jz 11f",
+            "9:",
+            "cmp {rem:e}, 2",
+            "jb 10f",
+            "mov {buf:x}, word ptr [{src} + {rem} - 2]",
+            "mov word ptr [{dest} + {rem} - 2], {buf:x}",
+            "sub {rem:e}, 2",
+            "jz 11f",
+            "10:",
+            "cmp {rem:e}, 1",
+            "jb 11f",
+            "mov {buf:l}, byte ptr [{src} + {rem} - 1]",
+            "mov byte ptr [{dest} + {rem} - 1], {buf:l}",
+            "11:",
+            src = in(reg) src,
+            dest = in(reg) dest,
+            rem = inout(reg) rem => _,
+            buf = out(reg) _,
+            options(nostack),
+        );
+    }
+}
+
+/// append `data` to `buf`, assuming `data` is less than 32 bytes and that `buf` has enough space
+/// remaining to hold all bytes in `data`.
+///
+/// Safety: callers must ensure that `buf.capacity() - buf.len() >= data.len()`.
+#[inline(always)]
+pub unsafe fn append_string_lt_32_unchecked(buf: &mut alloc::string::String, data: &str) {
+    // Safety: we are appending only valid utf8 strings to `self.buf`, as `s` is known to
+    // be valid utf8
+    let buf = unsafe { buf.as_mut_vec() };
+    let new_bytes = data.as_bytes();
+
+    unsafe {
+        let dest = buf.as_mut_ptr().offset(buf.len() as isize);
+        let src = new_bytes.as_ptr();
+
+        let rem = new_bytes.len() as isize;
+
+        // set_len early because there is no way to avoid the following asm!() writing that
+        // same number of bytes into buf
+        buf.set_len(buf.len() + new_bytes.len());
+
+        core::arch::asm!(
+            "6:",
+            "cmp {rem:e}, 16",
+            "jb 7f",
+            "mov {buf:r}, qword ptr [{src} + {rem} - 16]",
+            "mov qword ptr [{dest} + {rem} - 16], {buf:r}",
+            "mov {buf:r}, qword ptr [{src} + {rem} - 8]",
+            "mov qword ptr [{dest} + {rem} - 8], {buf:r}",
+            "sub {rem:e}, 16",
+            "jz 11f",
+            "7:",
+            "cmp {rem:e}, 8",
+            "jb 8f",
+            "mov {buf:r}, qword ptr [{src} + {rem} - 8]",
+            "mov qword ptr [{dest} + {rem} - 8], {buf:r}",
+            "sub {rem:e}, 8",
+            "jz 11f",
+            "8:",
+            "cmp {rem:e}, 4",
+            "jb 9f",
+            "mov {buf:e}, dword ptr [{src} + {rem} - 4]",
+            "mov dword ptr [{dest} + {rem} - 4], {buf:e}",
+            "sub {rem:e}, 4",
+            "jz 11f",
+            "9:",
+            "cmp {rem:e}, 2",
+            "jb 10f",
+            "mov {buf:x}, word ptr [{src} + {rem} - 2]",
+            "mov word ptr [{dest} + {rem} - 2], {buf:x}",
+            "sub {rem:e}, 2",
+            "jz 11f",
+            "10:",
+            "cmp {rem:e}, 1",
+            "jb 11f",
+            "mov {buf:l}, byte ptr [{src} + {rem} - 1]",
+            "mov byte ptr [{dest} + {rem} - 1], {buf:l}",
+            "11:",
+            src = in(reg) src,
+            dest = in(reg) dest,
+            rem = inout(reg) rem => _,
+            buf = out(reg) _,
+            options(nostack),
+        );
+    }
+}