Add .ds directive

3 files changed, 55 insertions, 0 deletions

diff --git a/README.md b/README.md
index 9c0f625..b00e1a9 100644
--- a/README.md
+++ b/README.md
@@ -294,6 +294,9 @@ and `>`for the high byte.
 .dw imm [, imm]  
 Literal word (16-bit value).
 
+.ds count, imm  
+Generates `count` bytes with value `imm`.
+
 .equ id value  
 Define an ID assigning a constant value. When the id is used, it will be replaced with its value.
 
diff --git a/game/main.asm b/game/main.asm
index 4b9a81f..8373f37 100644
--- a/game/main.asm
+++ b/game/main.asm
@@ -267,6 +267,9 @@ player_coord:
     .dw player_sprite
     .dw player_update
 
+    ; 16 entities
+    .ds 112, 0
+
     ; end of list
     .db ET_END
 
diff --git a/tr8as.c b/tr8as.c
index cfaa80b..0237683 100644
--- a/tr8as.c
+++ b/tr8as.c
@@ -770,6 +770,54 @@ static uint8_t parse_dw(As *as, char **c)
     return 1;
 }
 
+static uint8_t parse_ds(As *as, char **c)
+{
+    char word[MAX_ID + 1];
+    uint8_t wlen;
+    uint16_t count = 0xff, imm = 0xff;
+
+    /* .ds count, imm */
+
+    if (!next_word(as, c, word, &wlen))
+        return 0;
+
+    if (wlen == 0)
+        return error_l("Syntax error", &as->loc, "expected count");
+
+    if (!next_imm(as, word, &count))
+        return error_l("Syntax error", &as->loc, "expected count");
+
+    *c = skip_whitespace(*c);
+    if (**c != ',')
+        return error_l("Syntax error", &as->loc, "expected ,");
+    (*c)++;
+
+    if (!next_word(as, c, word, &wlen))
+        return 0;
+
+    if (wlen == 0)
+        return error_l("Syntax error", &as->loc, "expected immediate");
+
+    if (next_imm(as, word, &count))
+    {
+        if (imm > 0xff)
+            return error_l("Overflow in immediate", &as->loc, word);
+    }
+    else
+        return error_l("Syntax error", &as->loc, "expected immediate");
+
+    if (as->addr + count > UINT16_MAX)
+        return error_l("Memory overflow", &as->loc, "output is more than 65535 bytes");
+
+    for (uint16_t i = 0; i < count; i++)
+        as->out[as->addr++] = imm & 0xff;
+
+    if (as->addr > as->size)
+        as->size = as->addr;
+
+    return 1;
+}
+
 static uint8_t parse_nop(As *as, char **c)
 {
     /* NOP */
@@ -1530,6 +1578,7 @@ static InstParse insts[] =
     { ".equ", parse_equ },
     { ".db", parse_db },
     { ".dw", parse_dw },
+    { ".ds", parse_ds },
     { "halt", parse_halt },
     { "push", parse_push },
     { "port", parse_port },