dijk

bitset2.c

@@ -0,0 +1,15 @@
+#include <stddef.h>
+#include <stdint.h>
+
+#define BITSET_WORD_BITS (sizeof(bitset_word_t) * 8U)
+#define BITSET_WORD(idx) ((uintptr_t *)(bits))[(idx) / BITSET_WORD_BITS]
+#define BITSET_MASK(idx) ((uintptr_t)1 << ((idx) % BITSET_WORD_BITS))
+
+#define BITSET_SET(bits, idx)   (BITSET_WORD(idx) |= BITSET_MASK(idx))
+#define BITSET_CLEAR(bits, idx) (BITSET_WORD(idx) &= ~BITSET_MASK(idx))
+#define BITSET_FLIP(bits, idx)  (BITSET_WORD(idx) ^= BITSET_MASK(idx))
+#define BITSET_TEST(bits, idx)  (!!((BITSET_WORD(idx) & BITSET_MASK(idx)))) /* forces 0/1 */
+// #define BITSET_PUT(bits, idx, v)   do { if (v) BITSET_SET(bits,idx); else BITSET_CLEAR(bits,idx); } while(0)
+int main(void) {
+    return 0;
+}

dijk.c

@@ -0,0 +1,188 @@
+/* SPDX-License-Identifier: MIT */
+
+/*
+ * Imbus 2025
+ *
+ * PQ-less dijkstra in quadratic complexity
+ */
+
+#include <limits.h>
+#include <stdio.h>
+
+#define DIM 26
+
+#define A 0
+#define B 1
+#define C 2
+#define D 3
+#define E 4
+#define F 5
+#define G 6
+#define H 7
+#define I 8
+#define J 9
+#define K 10
+#define L 11
+#define M 12
+#define N 13
+#define O 14
+#define P 15
+#define Q 16
+#define R 17
+#define S 18
+#define T 19
+#define U 20
+#define V 21
+#define W 22
+#define X 23
+#define Y 24
+#define Z 25
+
+/* Node to character */
+#define ntoch(n) ('A' + (char)(n % 26))
+
+/* Some helpers */
+#define set_dist(from, to, d) g[((int)from)][((int)to)] = (int)d
+#define get_dist(from, to)    g[((int)from)][((int)to)]
+
+/* Adjacency matrix */
+int g[DIM][DIM] = {};
+
+void printmat(int mat[DIM][DIM]) {
+    printf("## ");
+    for (int h = 0; h < DIM; h++) printf("%c ", ntoch(h));
+    printf("\n");
+    printf("  ");
+    for (int h = 0; h < DIM; h++) printf("%s", "__");
+    printf("\n");
+    for (int i = 0; i < DIM; i++) {
+        printf("%c |", ntoch(i));
+        for (int j = 0; j < DIM; j++) {
+            printf("%c ", ntoch(mat[i][j]));
+        }
+        printf("\n");
+    }
+}
+
+void dijkstra(int mat[DIM][DIM], int prev[DIM], int dist[DIM], int s) {
+    int visited[DIM] = {0};
+
+    for (int i = 0; i < DIM; i++) {
+        dist[i] = INT_MAX;
+        prev[i] = -1;
+    }
+
+    dist[s] = 0;
+    prev[s] = 0;
+
+    for (int i = 0; i < DIM; i++) {
+        // Pick first unvisited with smallest dist
+        int u = -1;
+        int min = INT_MAX;
+
+        for (int j = 0; j < DIM; j++) {
+            if (!visited[j] && dist[j] < min) {
+                min = dist[j];
+                u = j;
+            }
+        }
+
+        if (u == -1)
+            break;
+        visited[u] = 1;
+
+        for (int v = 0; v < DIM; v++) {
+            if (get_dist(u, v) > 0 && !visited[v]) {
+                if (dist[u] + get_dist(u, v) < dist[v]) {
+                    dist[v] = dist[u] + get_dist(u, v);
+                    prev[v] = u;
+                }
+            }
+        }
+    }
+}
+
+void path_reconstruct(int prev[DIM], int dist[DIM], int s, int t) {
+    if (dist[t] == INT_MAX) {
+        printf("No path from %c to %c\n", ntoch(s), ntoch(t));
+        return;
+    }
+
+    int path[DIM];
+    int len = 0;
+
+    // Walk backwards from target to source
+    for (int v = t; v != -1; v = prev[v]) {
+        path[len++] = v;
+        if (v == s)
+            break;
+    }
+
+    if (path[len - 1] != s) {
+        printf("No path from %c to %c\n", ntoch(s), ntoch(t));
+        return;
+    }
+
+    // Print path in correct order
+    printf("Path (cost %d): ", dist[t]);
+    for (int i = len - 1; i >= 0; i--) {
+        printf("%c", ntoch(path[i]));
+        if (i > 0)
+            printf(" -> ");
+    }
+    printf("\n");
+}
+
+void init_graph(void) {
+    set_dist(A, B, 4);
+    set_dist(A, C, 9);
+    set_dist(B, D, 2);
+    set_dist(B, E, 5);
+    set_dist(C, B, 2);
+    set_dist(C, F, 7);
+    set_dist(D, C, 1);
+    set_dist(E, C, 2);
+    set_dist(F, G, 3);
+    set_dist(G, H, 6);
+    set_dist(H, I, 1);
+    set_dist(I, J, 8);
+    set_dist(J, K, 4);
+    set_dist(K, L, 5);
+    set_dist(L, M, 2);
+    set_dist(M, N, 3);
+    set_dist(N, O, 7);
+    set_dist(O, P, 1);
+    set_dist(P, Q, 2);
+    set_dist(Q, R, 6);
+    set_dist(R, S, 3);
+    set_dist(S, T, 5);
+    set_dist(T, U, 2);
+    set_dist(U, V, 1);
+    set_dist(V, W, 4);
+    set_dist(W, X, 7);
+    set_dist(X, Y, 2);
+    set_dist(Y, Z, 3);
+    set_dist(Z, A, 8);
+}
+
+int main(void) {
+    for (int i = 0; i < DIM; i++) {
+        for (int j = 0; j < DIM; j++) {
+            g[i][j] = -1;
+        }
+    }
+
+    init_graph();
+
+    printmat(g);
+
+    int prev[DIM] = {0};
+    int dist[DIM] = {0};
+    dijkstra(g, prev, dist, A);
+
+    for (int k = 0; k < DIM; k++) {
+        printf("%c prev: %c\n", ntoch(k), ntoch(prev[k]));
+    }
+
+    path_reconstruct(prev, dist, A, Z);
+}

interfaces.c

@@ -0,0 +1,70 @@
+#include <math.h>
+#include <stdio.h>
+
+// Here's a basic interface for geometric shapes.
+typedef struct {
+    double (*area)(void *);
+    double (*perim)(void *);
+} geometry;
+
+// For our example we'll implement this interface on
+// `rect` and `circle` types.
+typedef struct {
+    double width, height;
+} rect;
+
+typedef struct {
+    double radius;
+} circle;
+
+// To implement an interface in C, we need to define functions
+// that match the function pointers in the interface.
+// Here we implement `geometry` on `rect`s.
+double rect_area(void *r) {
+    rect *rect_ptr = (rect *)r;
+    return rect_ptr->width * rect_ptr->height;
+}
+
+double rect_perim(void *r) {
+    rect *rect_ptr = (rect *)r;
+    return 2 * rect_ptr->width + 2 * rect_ptr->height;
+}
+
+// The implementation for `circle`s.
+double circle_area(void *c) {
+    circle *circle_ptr = (circle *)c;
+    return M_PI * circle_ptr->radius * circle_ptr->radius;
+}
+
+double circle_perim(void *c) {
+    circle *circle_ptr = (circle *)c;
+    return 2 * M_PI * circle_ptr->radius;
+}
+
+// If a variable has an interface type, then we can call
+// methods that are in the named interface. Here's a
+// generic `measure` function taking advantage of this
+// to work on any `geometry`.
+void measure(void *g, geometry *geom) {
+    printf("Area: %f\n", geom->area(g));
+    printf("Perimeter: %f\n", geom->perim(g));
+}
+
+int main() {
+    rect   r = {.width = 3, .height = 4};
+    circle c = {.radius = 5};
+
+    // The `circle` and `rect` struct types both
+    // implement the `geometry` interface so we can use
+    // instances of these structs as arguments to `measure`.
+    geometry rect_geometry = {rect_area, rect_perim};
+    geometry circle_geometry = {circle_area, circle_perim};
+
+    printf("Rectangle:\n");
+    measure(&r, &rect_geometry);
+
+    printf("\nCircle:\n");
+    measure(&c, &circle_geometry);
+
+    return 0;
+}

riscv-vm.c

@@ -0,0 +1,66 @@
+#include <assert.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#define PPN_MASK    (UINT64_MAX >> 20)
+
+#define PPN_TO_PA(PPN) ((PPN & PPN_MASK) << 12)
+#define PA_TO_PPN(PA)  (PA >> 12)
+
+#define ALIGN_UP(n, align)   (((n) + (align) - 1) & ~((align) - 1))
+#define ALIGN_DOWN(n, align) ((n) & ~((align) - 1))
+
+#define IS_ALIGNED(x, align)     (((uintptr_t)(x) & ((uintptr_t)(align) - 1)) == 0)
+#define IS_ALIGNED_ANY(x, align) (((uintptr_t)(x) % (uintptr_t)(align)) == 0)
+
+#define IS_POWER_OF_TWO(x) (((x) != 0) && (((x) & ((x) - 1)) == 0))
+#define IS_ALIGNED_POW2(x, align)                                                                                      \
+    (assert(IS_POWER_OF_TWO((uintptr_t)(align))), (((uintptr_t)(x) & ((uintptr_t)(align) - 1)) == 0))
+
+#define VM_MODE_SV39 (2 << 64)
+
+#define PTE_V (1 << 0)
+#define PTE_R (1 << 1)
+#define PTE_W (1 << 2)
+#define PTE_X (1 << 3)
+/* And so on... */
+
+#define IS_LEAF(PTE) ((PTE & (PTE_R | PTE_W | PTE_X)) != 0)
+
+#define PTE_PPN(PTE, LEVEL) (((PTE) >> (10 + ((LEVEL) * 9)) & 0x1FF))
+
+int main(void) {
+    assert(IS_ALIGNED(0, 1));
+    assert(IS_ALIGNED(8, 8));
+    assert(IS_ALIGNED(12, 4));
+    assert(!IS_ALIGNED(66, 16));
+    assert(!IS_ALIGNED(234, 4096));
+    assert(!IS_ALIGNED(4099, 4096));
+
+    assert(PPN_MASK == 0b11111111111111111111111111111111111111111111);
+    assert(PPN_MASK == 17592186044415);
+    assert(PPN_MASK == 0xFFFFFFFFFFF);
+
+    printf("%lu", PPN_TO_PA(0xAAAAAA));
+    assert(IS_ALIGNED(PPN_TO_PA(0xAAAAAAAAAAAA), 4096));
+
+    uint64_t pte = 0b11111111110000000001111111110000000001111111111;
+
+    assert(pte & PTE_V);
+    assert(pte & PTE_R);
+    assert(pte & PTE_W);
+    assert(pte & PTE_X);
+
+    assert(IS_LEAF(pte));
+
+    assert(PTE_PPN(pte, 0) == 0);
+    assert(PTE_PPN(pte, 1) == 0b111111111);
+    assert(PTE_PPN(pte, 2) == 0);
+    pte <<= 9;
+    assert(PTE_PPN(pte, 0) == 0b111111111);
+    assert(PTE_PPN(pte, 1) == 0);
+    assert(PTE_PPN(pte, 2) == 0b111111111);
+
+    assert(!IS_LEAF(pte)); // Rightmost bits are now shifted out
+
+}

socket_inet/Makefile

@@ -0,0 +1,19 @@
+CC ?= gcc
+CFLAGS ?= -Wall -g
+
+all: server.elf client.elf
+
+server.elf: server.c
+client.elf: client.c
+
+%.elf: %.c
+	@echo CC $@
+	@$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
+
+test: all
+	bash test.sh
+
+clean:
+	rm -f *.elf *.o
+
+.PHONY: test clean

socket_inet/client.c

@@ -0,0 +1,54 @@
+#include <arpa/inet.h>
+#include <netdb.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#define MAX  80
+#define PORT 8080
+
+void func(int sockfd) {
+    char buff[MAX];
+
+    for (;;) {
+        char *msg = "Ping\n";
+        write(sockfd, msg, sizeof(buff));
+
+        bzero(buff, sizeof(buff));
+        read(sockfd, buff, sizeof(buff));
+
+        printf("From Server : %s", buff);
+        if ((strncmp(buff, "exit", 4)) == 0) {
+            printf("Client Exit...\n");
+            break;
+        }
+
+        exit(0);
+    }
+}
+
+int main() {
+    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
+    if (sockfd == -1) {
+        printf("socket creation failed...\n");
+        exit(0);
+    }
+    printf("Socket successfully created..\n");
+
+    struct sockaddr_in servaddr;
+    bzero(&servaddr, sizeof(servaddr));
+    servaddr.sin_family = AF_INET;
+    servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");
+    servaddr.sin_port = htons(PORT);
+
+    if (connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) != 0) {
+        printf("connection with the server failed...\n");
+        exit(0);
+    }
+
+    func(sockfd);
+    close(sockfd);
+}

socket_inet/server.c

@@ -0,0 +1,73 @@
+#include <netdb.h>
+#include <netinet/in.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#define MAX  80
+#define PORT 8080
+
+void func(int connfd) {
+    char buff[MAX];
+
+    for (;;) {
+        bzero(buff, MAX);
+
+        ssize_t recv_n = recv(connfd, buff, sizeof(buff), 0);
+        if (recv_n >= MAX) {
+            /* Likely more data, realloc */
+        }
+
+        buff[recv_n - 1] = '\0';
+        printf("From client: %s\n", buff);
+        bzero(buff, MAX);
+
+        char *msg = "Hello!\n";
+        send(connfd, msg, strlen(msg), 0);
+
+        if (strncmp("exit", buff, 4) == 0) {
+            printf("Server Exit...\n");
+            break;
+        }
+    }
+}
+
+int main() {
+    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
+    if (sockfd == -1) {
+        printf("socket creation failed...\n");
+        exit(0);
+    }
+
+    struct sockaddr_in servaddr;
+    bzero(&servaddr, sizeof(servaddr));
+
+    servaddr.sin_family = AF_INET;
+    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
+    servaddr.sin_port = htons(PORT);
+
+    if ((bind(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr))) != 0) {
+        printf("socket bind failed...\n");
+        exit(0);
+    }
+
+    if ((listen(sockfd, 5)) != 0) {
+        printf("Listen failed...\n");
+        exit(0);
+    }
+
+    struct sockaddr_in cli;
+    socklen_t          len = sizeof(cli);
+
+    int connfd = accept(sockfd, (struct sockaddr *)&cli, &len);
+    if (connfd < 0) {
+        printf("server accept failed...\n");
+        exit(0);
+    }
+
+    func(connfd);
+    close(sockfd);
+}

socket_inet/socket.c

@@ -0,0 +1,73 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+#define SOCKET_PATH "/tmp/demosocket"
+#define BUF_SIZE    128
+
+int main(void) {
+    int                server_fd, client_fd;
+    struct sockaddr_un addr;
+    char               buf[BUF_SIZE];
+
+    // Clean up any leftover socket file
+    unlink(SOCKET_PATH);
+
+    // Create socket
+    server_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+    if (server_fd == -1) {
+        perror("socket");
+        exit(EXIT_FAILURE);
+    }
+
+    // Zero out and set up the address structure
+    memset(&addr, 0, sizeof(addr));
+    addr.sun_family = AF_UNIX;
+    strncpy(addr.sun_path, SOCKET_PATH, sizeof(addr.sun_path) - 1);
+
+    // Bind the socket to the path
+    if (bind(server_fd, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
+        perror("bind");
+        close(server_fd);
+        exit(EXIT_FAILURE);
+    }
+
+    // Listen for a connection
+    if (listen(server_fd, 1) == -1) {
+        perror("listen");
+        close(server_fd);
+        exit(EXIT_FAILURE);
+    }
+
+    printf("Server listening on %s...\n", SOCKET_PATH);
+
+    // Accept a connection
+    client_fd = accept(server_fd, NULL, NULL);
+    if (client_fd == -1) {
+        perror("accept");
+        close(server_fd);
+        exit(EXIT_FAILURE);
+    }
+
+    // Receive a message
+    ssize_t received = recv(client_fd, buf, BUF_SIZE - 1, 0);
+    if (received > 0) {
+        buf[received] = '\0';
+        printf("Received: %s", buf);
+
+        // Send a reply
+        const char *reply = "Got your message!\n";
+        send(client_fd, reply, strlen(reply), 0);
+    } else {
+        perror("recv");
+    }
+
+    // Clean up
+    close(client_fd);
+    close(server_fd);
+    unlink(SOCKET_PATH);
+    return 0;
+}

socket_inet/test.sh

@@ -0,0 +1,26 @@
+#!/bin/bash
+
+SOCKET_PATH="/tmp/demosocket"
+
+# Cleanup function to be run on exit
+cleanup() {
+    echo "Cleaning up..."
+    if [[ -n "$SERVER_PID" ]]; then
+        kill "$SERVER_PID" 2>/dev/null || true
+        wait "$SERVER_PID" 2>/dev/null || true
+    fi
+    rm -f "$SOCKET_PATH"
+}
+
+# Trap EXIT to ensure cleanup runs
+trap cleanup EXIT
+
+echo "Starting server..."
+./server.elf &
+SERVER_PID=$!
+
+# Wait briefly for the server to start
+sleep 0.2
+
+echo "Running client..."
+./client.elf