Add unicode_filter.c

Author: Numbersf

tools/unicode_filter.c

@@ -0,0 +1,190 @@
+// unicode_filter.c
+// Supports format 4 + format 12
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+
+#define MAX_RANGES 128
+
+typedef struct {
+    uint32_t start;
+    uint32_t end;
+} Range;
+
+typedef struct {
+    Range ranges[MAX_RANGES];
+    int count;
+} RangeList;
+
+// BE helpers
+static uint16_t r16(const uint8_t *b){ return (b[0]<<8)|b[1]; }
+static uint32_t r32(const uint8_t *b){ return (b[0]<<24)|(b[1]<<16)|(b[2]<<8)|b[3]; }
+static void w16(uint8_t *b,uint16_t v){ b[0]=(v>>8)&0xFF; b[1]=v&0xFF; }
+static void w32(uint8_t *b,uint32_t v){ b[0]=(v>>24)&0xFF; b[1]=(v>>16)&0xFF; b[2]=(v>>8)&0xFF; b[3]=v&0xFF; }
+
+// checksum
+uint32_t checksum(uint8_t *data,uint32_t len){
+    uint32_t sum=0;
+    uint32_t n=(len+3)&~3;
+
+    for(uint32_t i=0;i<n;i+=4){
+        uint32_t v=0;
+        if(i+3 < len){
+            v=r32(data+i);
+        }else{
+            uint8_t tmp[4]={0,0,0,0};
+            for(int j=0;j<4;j++)
+                if(i+j < len) tmp[j]=data[i+j];
+            v=r32(tmp);
+        }
+        sum+=v;
+    }
+    return sum;
+}
+
+// check if this range overlaps any delete range
+int should_delete(uint32_t start,uint32_t end,RangeList *list){
+    for(int i=0;i<list->count;i++){
+        if(!(end < list->ranges[i].start || start > list->ranges[i].end))
+            return 1;
+    }
+    return 0;
+}
+
+// format12 safe rebuild
+void rebuild_format12_safe(uint8_t *sub,RangeList *list){
+    uint32_t n = r32(sub+12);
+    uint8_t *grp = sub+16;
+    uint32_t writeIndex=0;
+
+    for(uint32_t i=0;i<n;i++){
+        uint8_t *g = grp + i*12;
+        uint32_t start = r32(g);
+        uint32_t end   = r32(g+4);
+
+        if(should_delete(start,end,list)){
+            continue;
+        }
+
+        if(writeIndex != i)
+            memcpy(grp+writeIndex*12,g,12);
+
+        writeIndex++;
+    }
+
+    w32(sub+12,writeIndex);
+}
+
+// format4 rebuild
+void rebuild_format4_safe(uint8_t *sub,RangeList *list){
+    uint16_t segCount = r16(sub+6)/2;
+    uint8_t *p = sub+14;
+
+    uint16_t *endCode = (uint16_t*)p;
+    p += segCount*2;
+
+    p += 2; // reservedPad
+
+    uint16_t *startCode = (uint16_t*)p;
+    p += segCount*2;
+
+    uint16_t *idDelta = (uint16_t*)p;
+    p += segCount*2;
+
+    uint16_t *idRangeOffset = (uint16_t*)p;
+    // glyphIdArray follows but we don't modify it
+
+    for(int i=0;i<segCount;i++){
+        uint32_t start = r16((uint8_t*)&startCode[i]);
+        uint32_t end   = r16((uint8_t*)&endCode[i]);
+
+        if(start == 0xFFFF) continue;
+
+        if(should_delete(start,end,list)){
+            w16((uint8_t*)&idDelta[i],0);
+            w16((uint8_t*)&idRangeOffset[i],0);
+        }
+    }
+}
+
+// fix checksumAdjustment in head
+void fix_font_checksum(uint8_t *buf,uint32_t size){
+    uint16_t numTables=r16(buf+4);
+    uint8_t *head=NULL;
+
+    for(int i=0;i<numTables;i++){
+        uint8_t *rec=buf+12+i*16;
+        if(!memcmp(rec,"head",4)){
+            head=buf+r32(rec+8);
+            break;
+        }
+    }
+
+    if(!head) return;
+
+    w32(head+8,0);
+    uint32_t sum=checksum(buf,size);
+    uint32_t adj=0xB1B0AFBA - sum;
+    w32(head+8,adj);
+}
+
+int main(int argc,char **argv){
+    if(argc<3){
+        printf("Usage: %s font.ttf U+XXXX-U+YYYY\n",argv[0]);
+        return 1;
+    }
+
+    RangeList list;
+    list.count=1;
+    sscanf(argv[2],"U+%x-U+%x",&list.ranges[0].start,&list.ranges[0].end);
+
+    int fd=open(argv[1],O_RDWR);
+    struct stat st;
+    fstat(fd,&st);
+
+    uint8_t *buf=mmap(NULL,st.st_size,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
+
+    uint16_t numTables=r16(buf+4);
+    uint32_t cmap_offset=0;
+    uint8_t *cmap_record=NULL;
+
+    for(int i=0;i<numTables;i++){
+        uint8_t *rec=buf+12+i*16;
+        if(!memcmp(rec,"cmap",4)){
+            cmap_offset=r32(rec+8);
+            cmap_record=rec;
+        }
+    }
+
+    uint16_t numSub=r16(buf+cmap_offset+2);
+    for(int i=0;i<numSub;i++){
+        uint8_t *rec=buf+cmap_offset+4+i*8;
+        uint32_t off=r32(rec+4);
+        uint8_t *sub=buf+cmap_offset+off;
+        uint16_t format=r16(sub);
+
+        if(format==12)
+            rebuild_format12_safe(sub,&list);
+        if(format==4)
+            rebuild_format4_safe(sub,&list);
+    }
+
+    uint32_t cmap_len=r32(cmap_record+12);
+    uint32_t sum=checksum(buf+cmap_offset,cmap_len);
+    w32(cmap_record+4,sum);
+
+    fix_font_checksum(buf,st.st_size);
+
+    msync(buf,st.st_size,MS_SYNC);
+    munmap(buf,st.st_size);
+    close(fd);
+
+    printf("SAFE CMAP REBUILD COMPLETE\n");
+    return 0;
+}