initial commit

5 files changed, 82 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..28151d0
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+*.o
+bf
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..4e10a2a
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,5 @@
+bf: bf.c
+	$(CC) -O3 -Wall -Wextra -std=c89 -Wpedantic -o $@ $<
+
+clean:
+	rm -f bf
diff --git a/README.md b/README.md
index ed7fe69..a528f63 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,15 @@
 # bf
 A very small Brainfuck interpreter
+
+To build, simply run make.
+
+Running the interpreter is simple:
+
+    $ ./bf input.bf
+
+The interpreter purposely does no error checking. If you don't specify an
+input file, it will crash. If there is an error reading the input file, it
+will crash.
+
+Program size is fixed at the same size as data space, which is controlled by
+`#define S`.
diff --git a/bf.c b/bf.c
new file mode 100644
index 0000000..ddec8f5
--- /dev/null
+++ b/bf.c
@@ -0,0 +1,19 @@
+#include <stdio.h>
+#define S (1<<16)
+#define I a[1]
+#define D a[0]
+#define C case
+#define B break
+static char d[S], p[S];
+int main(int i, char *a[]) {
+ fread(p, 1, S, fopen(I, "r"));
+ for (D = d, I = p; I < p + S; I++) {
+  switch (i = *I) {
+  C '[': C ']': for (i = '\\' - *I; i < 0 ? *D : !*D; i += *(I += i > 0 ? 1 : -1) == '[' ? 1 : *I == ']' ? -1 : 0); B;
+  C '+': C '-': *D -= i - ','; B;
+  C '<': C '>': D += i - '='; B;
+  C ',': *D = getchar(); B;
+  C '.': putchar(*D); B;
+  }
+ }
+}
diff --git a/hello.bf b/hello.bf
new file mode 100644
index 0000000..df6f0a2
--- /dev/null
+++ b/hello.bf
@@ -0,0 +1,43 @@
+[ This program prints "Hello World!" and a newline to the screen, its
+  length is 106 active command characters. [It is not the shortest.]
+
+  This loop is an "initial comment loop", a simple way of adding a comment
+  to a BF program such that you don't have to worry about any command
+  characters. Any ".", ",", "+", "-", "<" and ">" characters are simply
+  ignored, the "[" and "]" characters just have to be balanced. This
+  loop and the commands it contains are ignored because the current cell
+  defaults to a value of 0; the 0 value causes this loop to be skipped.
+]
+++++++++               Set Cell #0 to 8
+[
+    >++++               Add 4 to Cell #1; this will always set Cell #1 to 4
+    [                   as the cell will be cleared by the loop
+        >++             Add 2 to Cell #2
+        >+++            Add 3 to Cell #3
+        >+++            Add 3 to Cell #4
+        >+              Add 1 to Cell #5
+        <<<<-           Decrement the loop counter in Cell #1
+    ]                   Loop till Cell #1 is zero; number of iterations is 4
+    >+                  Add 1 to Cell #2
+    >+                  Add 1 to Cell #3
+    >-                  Subtract 1 from Cell #4
+    >>+                 Add 1 to Cell #6
+    [<]                 Move back to the first zero cell you find; this will
+                        be Cell #1 which was cleared by the previous loop
+    <-                  Decrement the loop Counter in Cell #0
+]                       Loop till Cell #0 is zero; number of iterations is 8
+
+The result of this is:
+Cell No :   0   1   2   3   4   5   6
+Contents:   0   0  72 104  88  32   8
+Pointer :   ^
+
+>>.                     Cell #2 has value 72 which is 'H'
+>---.                   Subtract 3 from Cell #3 to get 101 which is 'e'
++++++++..+++.           Likewise for 'llo' from Cell #3
+>>.                     Cell #5 is 32 for the space
+<-.                     Subtract 1 from Cell #4 for 87 to give a 'W'
+<.                      Cell #3 was set to 'o' from the end of 'Hello'
++++.------.--------.    Cell #3 for 'rl' and 'd'
+>>+.                    Add 1 to Cell #5 gives us an exclamation point
+>++.                    And finally a newline from Cell #6