Better support for BLOBs

- Limbo command line shell supports e.g. `SELECT x'616263';`
- `EXPLAIN SELECT x'616263';` lists the opcode

Missing:

- Command line shell not entirely compatible with SQLite when blobs have
  non-printable characters in the middle (e.g. `SELECT x'610062';`)
- Python bindings not supported (incoming soon)

COMPAT.md

@@ -216,7 +216,7 @@ This document describes the SQLite compatibility status of Limbo:
 | BitAnd          | No     |
 | BitNot          | No     |
 | BitOr           | No     |
-| Blob            | No     |
+| Blob            | Yes    |
 | Checkpoint      | No     |
 | Clear           | No     |
 | Close           | No     |

cli/main.rs

@@ -275,7 +275,9 @@ fn query(
                                 Value::Integer(i) => print!("{}", i),
                                 Value::Float(f) => print!("{:?}", f),
                                 Value::Text(s) => print!("{}", s),
-                                Value::Blob(b) => print!("{:?}", b),
+                                Value::Blob(b) => {
+                                    print!("{}", String::from_utf8_lossy(b))
+                                }
                             }
                         }
                         println!();
@@ -305,7 +307,9 @@ fn query(
                                         Value::Integer(i) => i.to_string().cell(),
                                         Value::Float(f) => f.to_string().cell(),
                                         Value::Text(s) => s.cell(),
-                                        Value::Blob(b) => format!("{:?}", b).cell(),
+                                        Value::Blob(b) => {
+                                            format!("{}", String::from_utf8_lossy(b)).cell()
+                                        }
                                     })
                                     .collect(),
                             );

core/translate/expr.rs

@@ -1433,7 +1433,23 @@ pub fn translate_expr(
                 });
                 Ok(target_register)
             }
-            ast::Literal::Blob(_) => todo!(),
+            ast::Literal::Blob(s) => {
+                let bytes = s
+                    .as_bytes()
+                    .chunks_exact(2)
+                    .map(|pair| {
+                        // We assume that sqlite3-parser has already validated that
+                        // the input is valid hex string, thus unwrap is safe.
+                        let hex_byte = std::str::from_utf8(pair).unwrap();
+                        u8::from_str_radix(hex_byte, 16).unwrap()
+                    })
+                    .collect();
+                program.emit_insn(Insn::Blob {
+                    value: bytes,
+                    dest: target_register,
+                });
+                Ok(target_register)
+            }
             ast::Literal::Keyword(_) => todo!(),
             ast::Literal::Null => {
                 program.emit_insn(Insn::Null {

core/vdbe/explain.rs

@@ -470,6 +470,20 @@ pub fn insn_to_str(
                 0,
                 format!("r[{}]='{}'", dest, value),
             ),
+            Insn::Blob { value, dest } => (
+                "Blob",
+                0,
+                *dest as i32,
+                0,
+                OwnedValue::Blob(Rc::new(value.clone())),
+                0,
+                format!(
+                    "r[{}]={} (len={})",
+                    dest,
+                    String::from_utf8_lossy(value),
+                    value.len()
+                ),
+            ),
             Insn::RowId { cursor_id, dest } => (
                 "RowId",
                 *cursor_id as i32,

core/vdbe/mod.rs

@@ -279,6 +279,12 @@ pub enum Insn {
         dest: usize,
     },
 
+    // Write a blob value into a register.
+    Blob {
+        value: Vec<u8>,
+        dest: usize,
+    },
+
     // Read the rowid of the current row.
     RowId {
         cursor_id: CursorID,
@@ -1074,6 +1080,10 @@ impl Program {
                     state.registers[*dest] = OwnedValue::Text(Rc::new(value.into()));
                     state.pc += 1;
                 }
+                Insn::Blob { value, dest } => {
+                    state.registers[*dest] = OwnedValue::Blob(Rc::new(value.clone()));
+                    state.pc += 1;
+                }
                 Insn::RowId { cursor_id, dest } => {
                     let cursor = cursors.get_mut(cursor_id).unwrap();
                     if let Some(ref rowid) = cursor.rowid()? {

testing/scalar-functions.test

@@ -395,14 +395,13 @@ do_execsql_test typeof-real {
   SELECT typeof(1.0);
 } {real}
 
-# TODO: Uncomment when blobs are better supported
-# do_execsql_test typeof-blob {
-#   SELECT typeof(x'61');
-# } {blob}
-#
-# do_execsql_test typeof-blob-empty {
-#   SELECT typeof(x'');
-# } {blob}
+do_execsql_test typeof-blob {
+  SELECT typeof(x'61');
+} {blob}
+
+do_execsql_test typeof-blob-empty {
+  SELECT typeof(x'');
+} {blob}
 
 do_execsql_test typeof-sum-integer {
   SELECT typeof(sum(age)) from users;

testing/select.test

@@ -11,6 +11,18 @@ do_execsql_test select-const-2 {
   SELECT 2
 } {2}
 
+do_execsql_test select-blob-empty {
+  SELECT x'';
+} {}
+
+do_execsql_test select-blob-ascii {
+  SELECT x'6C696D626f';
+} {limbo}
+
+do_execsql_test select-blob-emoji {
+  SELECT x'F09FA680';
+} {🦀}
+
 do_execsql_test select-limit-0 {
   SELECT id FROM users LIMIT 0;
 } {}