From deeaf5134dcd156500436ad57ba3d6e814a21849 Mon Sep 17 00:00:00 2001
From: batleram <batleram@gmail.com>
Date: Sat, 24 Oct 2026 17:28:26 -0400
Subject: Hardcode templating ~800ms

---
 .gitignore  |  1 +
 Makefile    |  7 +++----
 calc.c      | 59 ++++++++++++++++++++++++++++++++++++++++++-----------------
 calc.h      |  3 +++
 itoa_gen.py | 15 +++++++++++++++
 5 files changed, 64 insertions(+), 21 deletions(-)
 create mode 100644 itoa_gen.py

diff --git a/.gitignore b/.gitignore
index d629681..b932cae 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 *.json
 calc
+itoa_lut.h
diff --git a/Makefile b/Makefile
index 75b6c76..7d75e27 100644
--- a/Makefile
+++ b/Makefile
@@ -1,13 +1,12 @@
 
 .PHONY: build
 
-build: calc.c
+build: calc.c lut
 	clang -o calc -O3 -ggdb ./calc.c
 
 bench: build
 	./calc 10.0.0.0/8 2
 
-bench2: build
-	./calc 10.0.0.0/6 2
-
+lut: itoa_gen.py
+	python3 ./itoa_gen.py
 
diff --git a/calc.c b/calc.c
index 2f533b1..ddcfe95 100644
--- a/calc.c
+++ b/calc.c
@@ -1,4 +1,5 @@
 #include "calc.h"
+#include "itoa_lut.h"
 #include <time.h>
 #include <errno.h>
 #include <stdint.h>
@@ -27,6 +28,25 @@ uint32_t subnetmask_for_netspace(unsigned int desired_netspace) {
     return start;
 }
 
+void write_ip(char **chunk_ptr, uint32_t ip) {
+    // local ptr so we don't have to deref every time
+    char *ptr = *chunk_ptr;
+    LutEntry e = {.bits = itoa_lut[(ip >> 24) & 0xff]};
+    WRITE_STR(ptr, e.fields.chars, e.fields.len)
+    ptr[0] = '.';
+    ptr += 1;
+    e.bits = itoa_lut[(ip >> 16) & 0xff];
+    WRITE_STR(ptr, e.fields.chars, e.fields.len)
+    ptr[0] = '.';
+    ptr += 1;
+    e.bits = itoa_lut[(ip >> 8) & 0xff];
+    WRITE_STR(ptr, e.fields.chars, e.fields.len)
+    ptr[0] = '.';
+    ptr += 1;
+    e.bits = itoa_lut[ip & 0xff];
+    WRITE_STR(ptr, e.fields.chars, e.fields.len)
+    *chunk_ptr = ptr;
+}
 
 int main(int argc, char** argv) {
     struct timespec start;
@@ -64,31 +84,36 @@ int main(int argc, char** argv) {
     fprintf(out, "[\n"); // file start
     uint32_t offset = 0;
     int i = 0;
+    char chunk[1024] = {0}; 
     while (i<req.count) {
         const uint32_t network = req.network + offset;
         const uint32_t first = network + 1;
         const uint32_t broadcast = first + ips_per_subnet - 2;
         const uint32_t last = broadcast - 1;
         offset += ips_per_subnet;
+        char* chunk_ptr = chunk;
+        WRITE_STR(chunk_ptr,  "\t{\n\t\t\"Reseau\": \"", 16)
+        write_ip(&chunk_ptr, network);
+        WRITE_STR(chunk_ptr,  "\",\n", 3)
+        WRITE_STR(chunk_ptr,  "\t\t\"Premiere\": \"", 15)
+        write_ip(&chunk_ptr, first);
+        WRITE_STR(chunk_ptr,  "\",\n", 3)
+        WRITE_STR(chunk_ptr,  "\t\t\"Derniere\": \"", 15)
+        write_ip(&chunk_ptr, last);
+        WRITE_STR(chunk_ptr,  "\",\n", 3)
+        WRITE_STR(chunk_ptr,  "\t\t\"Broadcast\": \"", 16)
+        write_ip(&chunk_ptr, broadcast);
+        WRITE_STR(chunk_ptr,  "\",\n", 3)
+        WRITE_STR(chunk_ptr,  "\t\t\"Nbr\": \"", 10)
+        LutEntry e = {.bits = itoa_lut[ips_per_subnet - 2]};
+        WRITE_STR(chunk_ptr, e.fields.chars, e.fields.len);
         if (i+1 == req.count) {
-            fprintf(out,
-                    "\t{\n\t\t\"Reseau\": \"%hu.%hu.%hu.%hu\",\n\t\t\"Premiere\": \"%hu.%hu.%hu.%hu\",\n\t\t\"Derniere\": \"%hu.%hu.%hu.%hu\",\n\t\t\"Broadcast\": \"%hu.%hu.%hu.%hu\",\n\t\t\"Nbr\": \"%hu\"\n\t}\n",
-                    UINT_TO_SEGMENTS(network),
-                    UINT_TO_SEGMENTS(first),
-                    UINT_TO_SEGMENTS(last),
-                    UINT_TO_SEGMENTS(broadcast),
-                    ips_per_subnet - 2
-                   );
-            break;
+            WRITE_STR(chunk_ptr,  "\"\n\t}\n", 5)
+        }else {
+            WRITE_STR(chunk_ptr,  "\"\n\t},\n", 6)
         }
-        fprintf(out,
-                "\t{\n\t\t\"Reseau\": \"%hu.%hu.%hu.%hu\",\n\t\t\"Premiere\": \"%hu.%hu.%hu.%hu\",\n\t\t\"Derniere\": \"%hu.%hu.%hu.%hu\",\n\t\t\"Broadcast\": \"%hu.%hu.%hu.%hu\",\n\t\t\"Nbr\": \"%hu\"\n\t},\n",
-                UINT_TO_SEGMENTS(network),
-                UINT_TO_SEGMENTS(first),
-                UINT_TO_SEGMENTS(last),
-                UINT_TO_SEGMENTS(broadcast),
-                ips_per_subnet - 2
-               );
+
+        fwrite(chunk, sizeof(char), chunk_ptr - chunk, out);
         i++;
     }
     fprintf(out, "]"); // file end
diff --git a/calc.h b/calc.h
index ea01529..fd6f222 100644
--- a/calc.h
+++ b/calc.h
@@ -2,10 +2,13 @@
 
 #define UINT_TO_SEGMENTS(i) (i>>24 & 0xff),(i>>16 & 0xff),(i>>8 & 0xff),(i & 0xff)
 
+#define WRITE_STR(ptr, str, len) for (int i=0; i<len; i++){ptr[0]=str[i]; ptr++;}
+
 int print_usage();
 uint32_t calc_netmask(unsigned int cidr);
 uint32_t segments_to_ip(unsigned int segments[4]);
 uint32_t cidr_for_netspace(unsigned int desired_netspace);
+void write_ip(char **chunk_ptr, uint32_t ip);
 
 typedef struct {
     uint32_t network;
diff --git a/itoa_gen.py b/itoa_gen.py
new file mode 100644
index 0000000..0437c62
--- /dev/null
+++ b/itoa_gen.py
@@ -0,0 +1,15 @@
+with open("itoa_lut.h", "w") as f:
+    f.write("#include <stdint.h>\n")
+    f.write("typedef union { struct { char chars[3]; uint8_t len; } fields; uint32_t bits; } LutEntry;\n")
+    f.write("const uint32_t itoa_lut[256] = {")
+    out = []
+    for i in range(0, 256):
+        running=len(str(i))
+        for j in reversed(range(3)):
+            running = running << 8
+            if j < len(str(i)):
+                running += ord(str(i)[j])
+        out.append(hex(running))
+    f.write(", ".join(out))
+    f.write("};")
+
-- 
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