Rewrite emulatorv1.0.0-alpha1

This is a complete rewrite and restructure of the entire emulator
project, as part of the effort in locking down the Bedrock specification
and in creating much better tooling for creating and using Bedrock
programs.

This commit adds a command-line argument scheme, an embedded assembler,
a headless emulator for use in non-graphical environments, deferred
window creation for programs that do not access the screen device,
and new versions of phosphor and bedrock-core. The new version of
phosphor supports multi-window programs, which will make it possible to
implement program forking in the system device later on, and the new
version of bedrock-core implements the final core specification.

1 files changed, 136 insertions, 0 deletions

diff --git a/src/metadata.rs b/src/metadata.rs
new file mode 100644
index 0000000..7130517
--- /dev/null
+++ b/src/metadata.rs
@@ -0,0 +1,136 @@
+use phosphor::Colour;
+
+
+pub fn parse_metadata(bytecode: &[u8]) -> Option<ProgramMetadata> {
+    MetadataParser::from_bytecode(bytecode).parse()
+}
+
+
+struct MetadataParser<'a> {
+    bytecode: &'a [u8],
+}
+
+impl<'a> MetadataParser<'a> {
+    pub fn from_bytecode(bytecode: &'a [u8]) -> Self {
+        Self { bytecode }
+    }
+
+    pub fn parse(self) -> Option<ProgramMetadata> {
+        macro_rules! array {
+            ($len:expr, $slice:expr) => {{
+                let mut array = [0; $len];
+                for i in 0..$len { array[i] = *$slice.get(i).unwrap_or(&0); }
+                array
+            }};
+        }
+
+        if self.range(0x00, 3) != &[0x41, 0x00, 0x20] {
+            return None;
+        }
+
+        let (name, version) = split_string(self.string(self.double(0x10)));
+        let authors = self.string(self.double(0x12)).map(|string| {
+            string.lines().map(|line| {
+                let (name, year) = split_string(Some(line.to_string()));
+                Author { name: name.unwrap(), year }
+            }).collect()
+        });
+
+        Some( ProgramMetadata {
+            bedrock_string: array!(7, self.range(0x03, 7)),
+            program_memory_size: match self.double(0x0a) {
+                0 => 65536, double => double as usize },
+            working_stack_size: match self.byte(0x0c) {
+                0 => 256, byte => byte as usize },
+            return_stack_size: match self.byte(0x0d) {
+                0 => 256, byte => byte as usize },
+            required_devices: self.double(0x0e),
+            name,
+            version,
+            authors,
+            description: self.string(self.double(0x14)),
+            path_buffer: match self.double(0x16) {
+                0 => None, addr => Some(addr as usize) },
+            small_icon: match self.double(0x18) {
+                0 => None, addr => Some(array!(72, self.range(addr, 72))) },
+            large_icon: match self.double(0x1a) {
+                0 => None, addr => Some(array!(512, self.range(addr, 512))) },
+            bg_colour: parse_colour(self.double(0x1c)),
+            fg_colour: parse_colour(self.double(0x1e)),
+        } )
+    }
+
+    fn byte(&self, address: u16) -> u8 {
+        *self.bytecode.get(address as usize).unwrap_or(&0)
+    }
+
+    fn double(&self, address: u16) -> u16 {
+        u16::from_be_bytes([
+            *self.bytecode.get(address as usize).unwrap_or(&0),
+            *self.bytecode.get(address as usize + 1).unwrap_or(&0),
+        ])
+    }
+
+    fn range(&self, address: u16, length: usize) -> &[u8] {
+        let start = address as usize;
+        let end = start + length;
+        self.bytecode.get(start..end).unwrap_or(&[])
+    }
+
+    fn string(&self, address: u16) -> Option<String> {
+        if address == 0 { return None; }
+        let start = address as usize;
+        let mut end = start;
+        while let Some(byte) = self.bytecode.get(end) {
+            match byte { 0 => break, _ => end += 1 }
+        }
+        let range = self.bytecode.get(start..end)?;
+        Some( String::from_utf8_lossy(range).to_string() )
+    }
+}
+
+fn split_string(string: Option<String>) -> (Option<String>, Option<String>) {
+    if let Some(string) = string {
+        match string.split_once(", ") {
+            Some((left, right)) => (Some(left.to_string()), Some(right.to_string())),
+            None => (Some(string), None),
+        }
+    } else {
+        (None, None)
+    }
+}
+
+fn parse_colour(double: u16) -> Option<Colour> {
+    let i = (double >> 12      ) as usize;
+    let r = (double >>  8 & 0xf) as u8 * 17;
+    let g = (double >>  4 & 0xf) as u8 * 17;
+    let b = (double       & 0xf) as u8 * 17;
+    match i {
+        0 => Some(Colour::from_rgb(r, g, b)),
+        _ => None,
+    }
+}
+
+
+pub struct ProgramMetadata {
+    pub bedrock_string: [u8; 7],
+    pub program_memory_size: usize,
+    pub working_stack_size: usize,
+    pub return_stack_size: usize,
+    pub required_devices: u16,
+    pub name: Option<String>,
+    pub version: Option<String>,
+    pub authors: Option<Vec<Author>>,
+    pub description: Option<String>,
+    pub path_buffer: Option<usize>,
+    pub small_icon: Option<[u8; 72]>,
+    pub large_icon: Option<[u8; 512]>,
+    pub bg_colour: Option<Colour>,
+    pub fg_colour: Option<Colour>,
+}
+
+
+pub struct Author {
+    pub name: String,
+    pub year: Option<String>,
+}