Created
August 14, 2020 03:36
-
-
Save MichaelSnowden/17b8bf805ea6100cdf0c2a5018476608 to your computer and use it in GitHub Desktop.
A pattern for applying a map function to a dag in C without using malloc.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
#include <stdio.h> | |
#include <zconf.h> | |
#include <stdlib.h> | |
#include <assert.h> | |
typedef struct IntNode { | |
int leaf; | |
int value; | |
int numChildren; | |
struct IntNode **children; | |
} IntNode; | |
typedef struct CharNode { | |
int leaf; | |
char value; | |
int numChildren; | |
struct CharNode **children; | |
} CharNode; | |
typedef struct Link { | |
const IntNode *input; | |
CharNode **output; | |
struct Link *next; | |
} Link; | |
void mapIntToChar(const IntNode *inputRoot, void done(CharNode *)) { | |
CharNode *outputRoot = NULL; | |
Link link0 = { | |
.input = inputRoot, | |
.output = &outputRoot, | |
.next = NULL, | |
}; | |
Link *head, *current, *tail; | |
head = current = tail = &link0; | |
while (current != NULL) { | |
// head <= current <= tail <= NULL | |
const IntNode *input = current->input; | |
CharNode **output = current->output; | |
current = current->next; | |
if (current == NULL) { | |
tail = NULL; | |
} | |
*output = alloca(sizeof(CharNode)); | |
(*output)->value = (char) (input->value + 'a'); | |
if (input->leaf) { | |
(*output)->leaf = 1; | |
} else { | |
(*output)->leaf = 0; | |
int numChildren = input->numChildren; | |
assert(numChildren >= 0); | |
(*output)->numChildren = numChildren; | |
(*output)->children = alloca(sizeof(CharNode *) * numChildren); | |
for (int i = 0; i < numChildren; ++i) { | |
const IntNode *childInput = input->children[i]; | |
CharNode **childOutput = (*output)->children + i; | |
// head <= current <= tail <= NULL | |
Link *link; | |
if (head == current) { | |
link = alloca(sizeof(Link)); | |
} else { | |
link = head; | |
head = head->next; | |
} | |
if (tail != NULL) { | |
tail->next = link; | |
} | |
tail = link; | |
if (current == NULL) { | |
current = tail; | |
} | |
if (head == NULL) { | |
head = current; | |
} | |
tail->input = childInput; | |
tail->output = childOutput; | |
tail->next = NULL; | |
} | |
} | |
} | |
done(outputRoot); | |
} | |
void printIntNode(IntNode *node, int indent) { | |
if (node == NULL) { | |
return; | |
} | |
printf("%*s%d\n", indent, "", node->value); | |
if (!node->leaf) { | |
for (int i = 0; i < node->numChildren; ++i) { | |
printIntNode(node->children[i], indent + 2); | |
} | |
} | |
} | |
void printCharNode(CharNode *node, int indent) { | |
if (node == NULL) { | |
return; | |
} | |
printf("%*c\n", indent + 1, node->value); | |
if (!node->leaf) { | |
for (int i = 0; i < node->numChildren; ++i) { | |
printCharNode(node->children[i], indent + 2); | |
} | |
} | |
} | |
#define INT_LEAF(i) \ | |
IntNode leaf ## i; \ | |
leaf ## i.leaf = 1;\ | |
leaf ## i.value = i; | |
#define INT_NODE(i, ...) \ | |
IntNode *children ## i[] = { __VA_ARGS__ };\ | |
IntNode node ## i; \ | |
node ## i.value = i; \ | |
node ## i.leaf = 0;\ | |
node ## i.numChildren = sizeof(children ## i) / sizeof(IntNode *); \ | |
node ## i.children = children ## i; | |
void callback(CharNode *root) { | |
printf("done!\n"); | |
printCharNode(root, 0); | |
} | |
int main() { | |
INT_LEAF(0) | |
INT_LEAF(1) | |
INT_LEAF(2) | |
INT_LEAF(3) | |
INT_LEAF(4) | |
INT_LEAF(5) | |
INT_LEAF(6) | |
INT_LEAF(7) | |
INT_NODE(8, &leaf0, &leaf1) | |
INT_NODE(9, &leaf2, &leaf3) | |
INT_NODE(10, &leaf4, &leaf5) | |
INT_NODE(11, &leaf6, &leaf7) | |
INT_NODE(12, &node8, &node9) | |
INT_NODE(13, &node10, &node11) | |
INT_NODE(14, &node12, &node13) | |
printIntNode(&node14, 0); | |
mapIntToChar(&node14, callback); | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment