Add initial barebones kernel and cross compiler container image

src/lib/printf.c

@@ -0,0 +1,171 @@
+
+#include <stdarg.h>
+#include <limits.h>
+
+#include "libc.h"
+
+typedef int (*printf_function)(struct printf_state* s, void* data);
+
+constexpr int EOF = -1;
+
+struct printf_state {
+    struct str str;
+    va_list ap;
+    size_t i;
+    int written;
+};
+
+static inline int ps_peek(struct printf_state* s)
+{
+    if (s->i == s->str.len) {
+        return EOF;
+    }
+    return s->str.data[s->i];
+}
+
+static inline int ps_get(struct printf_state* s)
+{
+    if (s->i == s->str.len) {
+        return EOF;
+    }
+    return s->str.data[s->i++];
+}
+
+static int print_long(unsigned long n, struct str alphabet, bool is_signed)
+{
+    constexpr size_t BUF_SZ = 21;
+    char buf[BUF_SZ];
+    size_t i = 0;
+
+    if (n == 0) {
+        terminal_putchar('0');
+        return 1;
+    }
+
+    bool is_negative = false;
+    if (is_signed) {
+        signed long signed_n = (signed long)n;
+        if (signed_n < 0) {
+            is_negative = true;
+            n = -signed_n;
+        }
+    }
+
+    if (is_negative)
+        terminal_putchar('-');
+
+    while (n) {
+        i += 1;
+        buf[BUF_SZ-i] = alphabet.data[n % alphabet.len];
+        n /= alphabet.len;
+    }
+
+    terminal_write((struct str){.data = &buf[BUF_SZ-i], .len = i});
+
+    return i;
+}   
+
+static int print_i16(struct printf_state* s)
+{
+    // int16_t is promoted to 'int' when passed through '...'
+    long n = va_arg(s->ap, int32_t);
+    return print_long(n, str_attach("0123456789"), true);
+}
+
+static int print_i32(struct printf_state* s)
+{
+    long n = va_arg(s->ap, int32_t);
+    return print_long(n, str_attach("0123456789"), true);
+}
+
+static int print_i64(struct printf_state* s)
+{
+    panic(str_attach("print_i64 not implemented on i686"));
+    long n = va_arg(s->ap, int64_t);
+    return print_long(n, str_attach("0123456789"), true);
+}
+
+static int print_u16(struct printf_state* s)
+{
+    // uint16_t is promoted to 'unsigned int' when passed through '...'
+    unsigned long n = va_arg(s->ap, unsigned int);
+    return print_long(n, str_attach("0123456789"), false);
+}
+
+static int print_u32(struct printf_state* s)
+{
+    unsigned long n = va_arg(s->ap, uint32_t);
+    return print_long(n, str_attach("0123456789"), false);
+}
+
+static int print_u64(struct printf_state* s)
+{
+    panic(str_attach("print_u64 not implemented on i686"));
+    unsigned long n = va_arg(s->ap, uint64_t);
+    return print_long(n, str_attach("0123456789"), false);
+}
+
+#pragma GCC diagnostic ignored "-Wmultichar"
+static int parse_format_cmd(struct printf_state* s)
+{
+    int c;
+    uint32_t cmd = 0;
+
+    constexpr uint32_t CHAR_MASK = (1<<CHAR_BIT)-1;
+
+    while (c = ps_get(s), c != EOF && c != '}') {
+        cmd <<= CHAR_BIT;
+        cmd |= c & CHAR_MASK;
+    }
+
+    if (c == EOF)
+        return -1;
+
+    switch (cmd) {
+        case 'i16': return print_i16(s);
+        case 'i32': return print_i32(s);
+        case 'i64': return print_i64(s);
+        case 'u16': return print_u16(s);
+        case 'u32': return print_u32(s);
+        case 'u64': return print_u64(s);
+        default:
+            terminal_write(str_attach("\nunknown cmd: "));
+            while (cmd) {
+                terminal_putchar(cmd & CHAR_MASK);
+                cmd >>= CHAR_BIT;
+            }
+            terminal_putchar('\n');
+            return -1;
+    }
+}
+
+int printf(struct str format, ...)
+{
+    int c;
+
+    struct printf_state s = {
+        .str = format,
+        .i = 0,
+        .written = 0,
+    };
+    va_start(s.ap, format);
+
+    while ((c = ps_get(&s)) != EOF) {
+        switch (c) {
+
+        case '{':
+            int ok = parse_format_cmd(&s);
+            if (ok == -1)
+                return -1;
+            s.written += ok;
+            break;
+
+        default:
+            terminal_putchar(c);
+            s.written += 1;
+            break;
+        }
+    }
+
+    return s.written;
+}