Assemble two instructions.

4 files changed, 66 insertions, 14 deletions

diff --git a/README.md b/README.md
index 7df1f4b..4eb7c2b 100644
--- a/README.md
+++ b/README.md
@@ -1,13 +1,12 @@
-# minias
+# dumbas
 
-An assembler for x86_64, written for fun and learning.
+A dumb assembler for x86_64, written for fun and learning.
 
 Goals:
 
 - A simple, tiny, fast implementation (in that order).
 - Assemble the output of [cproc](https://github.com/michaelforney/cproc)/[qbe](https://c9x.me/compile/).
 - Relocatable elf output.
-- Static linking only.
 
 Non Goals:
 
diff --git a/asmparser.peg b/asmparser.peg
new file mode 100644
index 0000000..77f90e5
--- /dev/null
+++ b/asmparser.peg
@@ -0,0 +1,11 @@
+%prefix "asmparser"
+
+%value "Parsev"
+
+program <- line* !.
+line <- s:stmt eol { srcpos = $0s; onstmt(s); }
+stmt <- i:instr { $$ = i; }
+instr <- "nop" { $$.instr = (Instr){.kind = ASM_NOP}; }
+       / "ret" { $$.instr = (Instr){.kind = ASM_RET}; }
+ws <- [ \t]*
+eol <- ws ("\n" / ! .)
diff --git a/minias.h b/dumbas.h
index 7ad5883..00f4fad 100644
--- a/minias.h
+++ b/dumbas.h
@@ -5,6 +5,26 @@
 #include <stdio.h>
 #include <unistd.h>
 
+typedef struct {
+  Elf64_Shdr hdr;
+  size_t capacity;
+  uint8_t *data;
+} Section;
+
+enum AsmKind {
+  ASM_NOP,
+  ASM_RET
+};
+
+typedef struct {
+  enum AsmKind kind;
+} Instr;
+
+typedef union {
+  enum AsmKind kind;
+  Instr instr;
+} Parsev;
+
 static void die(char *s) {
   write(STDERR_FILENO, s, strlen(s));
   exit(1);
diff --git a/main.c b/main.c
index e0bc8b7..0877d4a 100644
--- a/main.c
+++ b/main.c
@@ -1,15 +1,12 @@
-#include "minias.h"
+#include "dumbas.h"
 
-typedef struct {
-  Elf64_Shdr hdr;
-  size_t capacity;
-  uint8_t *data;
-} Section;
+int srcpos = 0;
 
 #define MAXSECTIONS 32
 static Section sections[MAXSECTIONS];
 static size_t nsections = 1; // first is reserved.
 
+static Section *cursection = NULL;
 static Section *shstrtab = NULL;
 static Section *strtab = NULL;
 static Section *symtab = NULL;
@@ -25,6 +22,10 @@ static void secappend(Section *s, uint8_t *bytes, size_t n) {
   s->hdr.sh_size += n;
 }
 
+static void secbyte(Section *s, uint8_t b) {
+  secappend(s, &b, 1);
+}
+
 static Elf64_Word elfstr(Section *sec, const char *s) {
   Elf64_Word i;
   for (i = 0; i < sec->hdr.sh_size; i++) {
@@ -45,16 +46,14 @@ static Section *newsection() {
 }
 
 static void initsections(void) {
-  uint8_t zb = 0;
-
   shstrtab = newsection();
-  secappend(shstrtab, &zb, 1);
+  secbyte(shstrtab, 0);
   shstrtab->hdr.sh_name = elfstr(shstrtab, ".shstrtab");
   shstrtab->hdr.sh_type = SHT_STRTAB;
   shstrtab->hdr.sh_entsize = 1;
 
   strtab = newsection();
-  secappend(strtab, &zb, 1);
+  secbyte(strtab, 0);
   strtab->hdr.sh_name = elfstr(shstrtab, ".strtab");
   strtab->hdr.sh_type = SHT_STRTAB;
   strtab->hdr.sh_entsize = 1;
@@ -122,8 +121,31 @@ static void outelf(void) {
   }
 }
 
-int main() {
+void onstmt(Parsev p) {
+  switch (p.kind) {
+  case ASM_NOP:
+    secbyte(cursection, 0x90);
+    break;
+  case ASM_RET:
+    secbyte(cursection, 0xc3);
+    break;
+  default:
+    die("unexpected kind");
+  }
+}
+
+#include "asmparser.c" // XXX resolve dependency cycle.
+
+void parse(void) {
+  asmparser_context_t *ctx = asmparser_create(NULL);
+  while (asmparser_parse(ctx, NULL));
+  asmparser_destroy(ctx);
+}
+
+int main(void) {
   initsections();
+  cursection = text;
+  parse();
   outelf();
   return 0;
 }
\ No newline at end of file