diff --git a/scan/scan_8int.c b/scan/scan_8int.c
index dba3be4..868faa0 100644
--- a/scan/scan_8int.c
+++ b/scan/scan_8int.c
@@ -1,8 +1,14 @@
 #include "scan.h"
 
 size_t scan_8int(const char* src,unsigned int* dest) {
-  unsigned long l;
-  size_t len=scan_8long(src,&l);
+  register const char *tmp=src;
+  register unsigned int l=0;
+  register unsigned char c;
+  while ((c=*tmp-'0')<8) {
+    if (l>>(sizeof(l)*8-3)) break;
+    l=l*8+c;
+    ++tmp;
+  }
   *dest=l;
-  return len;
+  return tmp-src;
 }
diff --git a/scan/scan_8longn.c b/scan/scan_8longn.c
index 61885d6..7d500d4 100644
--- a/scan/scan_8longn.c
+++ b/scan/scan_8longn.c
@@ -5,6 +5,7 @@ size_t scan_8longn(const char *src,size_t n,unsigned long *dest) {
   register unsigned long l=0;
   register unsigned char c;
   while (n-->0 && (c=*tmp-'0')<8) {
+    if (l>>(sizeof(l)*8-3)) break;
     l=l*8+c;
     ++tmp;
   }
diff --git a/scan/scan_8short.c b/scan/scan_8short.c
index b3cf0f3..b83837d 100644
--- a/scan/scan_8short.c
+++ b/scan/scan_8short.c
@@ -1,8 +1,14 @@
 #include "scan.h"
 
 size_t scan_8short(const char* src,unsigned short* dest) {
-  unsigned long l;
-  size_t len=scan_8long(src,&l);
+  register const char *tmp=src;
+  register unsigned short l=0;
+  register unsigned char c;
+  while ((c=*tmp-'0')<8) {
+    if (l>>(sizeof(l)*8-3)) break;
+    l=l*8+c;
+    ++tmp;
+  }
   *dest=l;
-  return len;
+  return tmp-src;
 }
diff --git a/scan/scan_int.c b/scan/scan_int.c
index 137cf55..4f82f0b 100644
--- a/scan/scan_int.c
+++ b/scan/scan_int.c
@@ -1,8 +1,38 @@
 #include "scan.h"
 
+static const unsigned int maxint = ((unsigned int)-1)>>1;
+
 size_t scan_int(const char* src,int* dest) {
-  long l;
-  size_t len=scan_long(src,&l);
-  if (len) *dest=l;
-  return len;
+  register const char *tmp;
+  register int l;
+  register unsigned char c;
+  int neg;
+  int ok;
+  tmp=src; l=0; ok=neg=0;
+  switch (*tmp) {
+  case '-': neg=1;
+  case '+': ++tmp;
+  }
+  while ((c=(unsigned char)(*tmp-'0'))<10) {
+    unsigned long int n;
+    /* we want to do: l=l*10+c
+     * but we need to check for integer overflow.
+     * to check whether l*10 overflows, we could do
+     *   if ((l*10)/10 != l)
+     * however, multiplication and division are expensive.
+     * so instead of *10 we do (l<<3) (i.e. *8) + (l<<1) (i.e. *2)
+     * and check for overflow on all the intermediate steps */
+    n=(unsigned int)l<<3; if ((n>>3)!=(unsigned int)l) break;
+    if (n+(l<<1) < n) break;
+    n+=l<<1;
+    if (n+c < n) break;
+    n+=c;
+    if (n > maxint+neg) break;
+    l=n;
+    ++tmp;
+    ok=1;
+  }
+  if (!ok) return 0;
+  *dest=(neg?-l:l);
+  return (size_t)(tmp-src);
 }
diff --git a/scan/scan_longn.c b/scan/scan_longn.c
index c6e913e..f1c0a92 100644
--- a/scan/scan_longn.c
+++ b/scan/scan_longn.c
@@ -1,5 +1,7 @@
 #include "scan.h"
 
+static const unsigned long maxlong = ((unsigned long)-1)>>1;
+
 size_t scan_longn(const char *src,size_t n,long *dest) {
   register const char *tmp;
   register long int l;
@@ -12,12 +14,26 @@ size_t scan_longn(const char *src,size_t n,long *dest) {
   case '-': neg=1;
   case '+': ++tmp;
   }
-  while (n-->0 && (c=*tmp-'0')<10) {
-    l=l*10+c;
+  while (n-->0 && (c=(unsigned char)(*tmp-'0'))<10) {
+    unsigned long int n;
+    /* we want to do: l=l*10+c
+     * but we need to check for integer overflow.
+     * to check whether l*10 overflows, we could do
+     *   if ((l*10)/10 != l)
+     * however, multiplication and division are expensive.
+     * so instead of *10 we do (l<<3) (i.e. *8) + (l<<1) (i.e. *2)
+     * and check for overflow on all the intermediate steps */
+    n=(unsigned long)l<<3; if ((n>>3)!=(unsigned long)l) break;
+    if (n+(l<<1) < n) break;
+    n+=l<<1;
+    if (n+c < n) break;
+    n+=c;
+    if (n > maxlong+neg) break;
+    l=n;
     ++tmp;
     ok=1;
   }
   if (!ok) return 0;
   *dest=(neg?-l:l);
-  return tmp-src;
+  return (size_t)(tmp-src);
 }
diff --git a/scan/scan_short.c b/scan/scan_short.c
index a029ccf..14051bd 100644
--- a/scan/scan_short.c
+++ b/scan/scan_short.c
@@ -1,8 +1,38 @@
 #include "scan.h"
 
+static const unsigned int maxshort = ((unsigned short)-1)>>1;
+
 size_t scan_short(const char* src,short* dest) {
-  long l;
-  size_t len=scan_long(src,&l);
-  *dest=l;
-  return len;
+  register const char *tmp;
+  register short l;
+  register unsigned char c;
+  int neg;
+  int ok;
+  tmp=src; l=0; ok=neg=0;
+  switch (*tmp) {
+  case '-': neg=1;
+  case '+': ++tmp;
+  }
+  while ((c=(unsigned char)(*tmp-'0'))<10) {
+    unsigned long int n;
+    /* we want to do: l=l*10+c
+     * but we need to check for integer overflow.
+     * to check whether l*10 overflows, we could do
+     *   if ((l*10)/10 != l)
+     * however, multiplication and division are expensive.
+     * so instead of *10 we do (l<<3) (i.e. *8) + (l<<1) (i.e. *2)
+     * and check for overflow on all the intermediate steps */
+    n=(unsigned int)l<<3; if ((n>>3)!=(unsigned int)l) break;
+    if (n+(l<<1) < n) break;
+    n+=l<<1;
+    if (n+c < n) break;
+    n+=c;
+    if (n > maxshort+neg) break;
+    l=n;
+    ++tmp;
+    ok=1;
+  }
+  if (!ok) return 0;
+  *dest=(neg?-l:l);
+  return (size_t)(tmp-src);
 }
diff --git a/scan/scan_ushort.c b/scan/scan_ushort.c
index 8b969a9..bdfd4fa 100644
--- a/scan/scan_ushort.c
+++ b/scan/scan_ushort.c
@@ -20,7 +20,7 @@ size_t scan_ushort(const char* src,unsigned short* dest) {
       n=l<<3; if ((n>>3)!=l) break;
       if (n+(l<<1) < n) break;
       n+=l<<1;
-      if (n+c < n) break;
+      if ((unsigned short)(n+c) < n) break;
       l=n+c;
       ++tmp;
     }
diff --git a/scan/scan_xint.c b/scan/scan_xint.c
index f55f9fc..5564a23 100644
--- a/scan/scan_xint.c
+++ b/scan/scan_xint.c
@@ -1,8 +1,13 @@
 #include "scan.h"
 
 size_t scan_xint(const char* src,unsigned int* dest) {
-  unsigned long l;
-  register int len=scan_xlong(src,&l);
+  register const char *tmp=src;
+  register unsigned int l=0;
+  register unsigned char c;
+  while ((l>>(sizeof(l)*8-4))==0 && (c=scan_fromhex(*tmp))<16) {
+    l=(l<<4)+c;
+    ++tmp;
+  }
   *dest=l;
-  return len;
+  return tmp-src;
 }
diff --git a/scan/scan_xlongn.c b/scan/scan_xlongn.c
index a24cf67..7618ac5 100644
--- a/scan/scan_xlongn.c
+++ b/scan/scan_xlongn.c
@@ -4,7 +4,7 @@ size_t scan_xlongn(const char *src,size_t n,unsigned long *dest) {
   register const char *tmp=src;
   register unsigned long l=0;
   register unsigned char c;
-  while (n-->0 && (c=scan_fromhex(*tmp))<16) {
+  while (n-->0 && (l>>(sizeof(l)*8-4))==0 && (c=scan_fromhex(*tmp))<16) {
     l=(l<<4)+c;
     ++tmp;
   }
diff --git a/scan/scan_xshort.c b/scan/scan_xshort.c
index a66ef5a..82c3cc6 100644
--- a/scan/scan_xshort.c
+++ b/scan/scan_xshort.c
@@ -1,8 +1,13 @@
 #include "scan.h"
 
 size_t scan_xshort(const char* src,unsigned short* dest) {
-  unsigned long l;
-  size_t len=scan_xlong(src,&l);
+  register const char *tmp=src;
+  register unsigned short l=0;
+  register unsigned char c;
+  while ((l>>(sizeof(l)*8-4))==0 && (c=scan_fromhex(*tmp))<16) {
+    l=(l<<4)+c;
+    ++tmp;
+  }
   *dest=l;
-  return len;
+  return tmp-src;
 }
diff --git a/test/marshal.c b/test/marshal.c
index 8a0f322..9b060c1 100644
--- a/test/marshal.c
+++ b/test/marshal.c
@@ -11,6 +11,17 @@ void zap() { size_t i; for (i=0; i<sizeof(buf); ++i) buf[i]='_'; }
 int main() {
   uint32_t x;
 
+  unsigned long long ull;
+  unsigned long ul;
+  unsigned int ui;
+  unsigned short us;
+  unsigned char uc;
+  signed long long ll;
+  signed long l;
+  signed int i;
+  signed short s;
+  signed char c;
+
   // check utf8 encoding
   zap(); assert(fmt_utf8(NULL,12345) == 3);
   zap(); assert(fmt_utf8(buf,12345) == 3 && byte_equal(buf,4,"\xe3\x80\xb9_"));
@@ -128,4 +139,71 @@ int main() {
   assert(fmt_escapecharquotedprintableutf8(NULL,0xf6)==6);	// =c3=b6
   zap(); assert(fmt_escapecharquotedprintableutf8(buf,0xf6)==6 && byte_equal(buf,7,"=c3=b6_"));
 
+  assert(scan_ulong("23",&ul)==2 && ul==23);
+  assert(scan_ulong("46halbe",&ul)==2 && ul==46);
+  if (sizeof(ul)==4) {
+    assert(scan_ulong("4294967295",&ul)==10 && ul==0xffffffff);
+    assert(scan_ulong("4294967296",&ul)==9 && ul==429496729);
+    assert(scan_xlong("ffffffff",&ul)==8 && ul==0xffffffff);
+    assert(scan_xlong("ffffffff0",&ul)==8 && ul==0xffffffff);
+    assert(scan_8long("37777777777",&ul)==11 && ul==0xffffffff);
+    assert(scan_8long("377777777771",&ul)==11 && ul==0xffffffff);
+
+    assert(scan_long("2147483647",&l)==10 && l==0x7fffffff);
+    assert(scan_long("02147483647",&l)==11 && l==0x7fffffff);
+    assert(scan_long("021474836470",&l)==11 && l==0x7fffffff);
+    assert(scan_long("+2147483647",&l)==11 && l==0x7fffffff);
+    assert(scan_long("+2147483648",&l)==10 && l==214748364);
+    assert(scan_long("-2147483647",&l)==11 && l==-2147483647);
+    assert(scan_long("-2147483648",&l)==11 && l==-2147483648);
+    assert(scan_long("-2147483649",&l)==10 && l==-214748364);
+
+  } else {
+    assert(scan_ulong("18446744073709551615",&ul)==20 && ul==0xffffffffffffffffull);
+    assert(scan_ulong("18446744073709551616",&ul)==19 && ul==1844674407370955161ull);
+    assert(scan_xlong("ffffffffffffffff",&ul)==16 && ul==0xffffffffffffffffull);
+    assert(scan_xlong("ffffffffffffffff0",&ul)==16 && ul==0xffffffffffffffffull);
+    assert(scan_8long("1777777777777777777777",&ul)==22 && ul==0xffffffffffffffffull);
+    assert(scan_8long("17777777777777777777770",&ul)==22 && ul==0xffffffffffffffffull);
+
+    assert(scan_long("9223372036854775807",&l)==19 && l==0x7fffffffffffffffll);
+    assert(scan_long("09223372036854775807",&l)==20 && l==0x7fffffffffffffffll);
+    assert(scan_long("092233720368547758070",&l)==20 && l==0x7fffffffffffffffll);
+    assert(scan_long("+9223372036854775807",&l)==20 && l==0x7fffffffffffffffll);
+    assert(scan_long("+9223372036854775808",&l)==19 && l==922337203685477580ll);
+    assert(scan_long("-9223372036854775807",&l)==20 && l==-9223372036854775807ll);
+    x=scan_long("-9223372036854775808",&l);
+    assert(scan_long("-9223372036854775808",&l)==20 && l==0x8000000000000000);
+    assert(scan_long("-9223372036854775809",&l)==19 && l==-922337203685477580ll);
+
+  }
+  assert(scan_uint("4294967295",&ui)==10 && ui==0xffffffff);
+  assert(scan_uint("4294967296",&ui)==9 && ui==429496729);
+  assert(scan_ushort("65535",&us)==5 && us==0xffff);
+  assert(scan_ushort("65536",&us)==4 && us==6553);
+
+  assert(scan_xint("0ffffffff",&ui)==9 && ui==0xffffffff);
+  assert(scan_xint("ffffffff0",&ui)==8 && ui==0xffffffff);
+  assert(scan_xshort("0ffff",&us)==5 && us==0xffff);
+  assert(scan_xshort("ffff1",&us)==4 && us==0xffff);
+
+  assert(scan_8int("037777777777",&ui)==12 && ui==0xffffffff);
+  assert(scan_8int("377777777771",&ui)==11 && ui==0xffffffff);
+  assert(scan_8short("00177777",&us)==8 && us==0xffff);
+  assert(scan_8short("1777771",&us)==6 && us==0xffff);
+
+  assert(scan_int("2147483647",&i)==10 && i==0x7fffffff);
+  assert(scan_int("02147483647",&i)==11 && i==0x7fffffff);
+  assert(scan_int("021474836470",&i)==11 && i==0x7fffffff);
+  assert(scan_int("+2147483647",&i)==11 && i==0x7fffffff);
+  assert(scan_int("+2147483648",&i)==10 && i==214748364);
+  assert(scan_int("-2147483647",&i)==11 && i==-2147483647);
+  assert(scan_int("-2147483648",&i)==11 && i==-2147483648);
+  assert(scan_int("-2147483649",&i)==10 && i==-214748364);
+
+  assert(scan_short("32767",&s)==5 && s==32767);
+  assert(scan_short("32768",&s)==4 && s==3276);
+  assert(scan_short("+032767",&s)==7 && s==32767);
+  assert(scan_short("-32768",&s)==6 && s==-32768);
+  assert(scan_short("-032769",&s)==6 && s==-3276);
 }