Move nonstring and memory APIs from lib/string/ to a new lib/memory/

[alejandro-colomar]

@ikerexxe It turns out it was less work than I thought, so we can do the movement already. Here it is.

See also memory.h(3head): https://www.kernel.org/pub/linux/docs/man-pages/book/man-pages-6.19.pdf#memory.h.3head.

---

Revisions:

v1b

• Update paragraph in the README. [@ikerexxe ]

$ git rd 
 1:  f65d2fe1b947 =  1:  f65d2fe1b947 lib/memory/README: Add symlink to the string README
 2:  a686e1b76ef7 !  2:  81219686b3fb lib/string/README: Reorganize the library in memory/ and string/
    @@ Commit message
         Signed-off-by: Alejandro Colomar <alx@kernel.org>
     
      ## lib/string/README ##
    -@@ lib/string/README: Specific guidelines:
    -   strings, separated in subdirectories by utility type.  In this
    -   section, we provide a broad overview.
    +@@ lib/string/README: Don't use some libc functions without Really Good Reasons:
    + 
    + Specific guidelines:
    + ====================
    ++  Under lib/memory/ we provide a set of functions to manipulate
    ++  bytes --mem*()-- and nonstrings --strn*()--.
    +   Under lib/string/ we provide a set of functions to manipulate
    +-  strings, separated in subdirectories by utility type.  In this
    +-  section, we provide a broad overview.
    ++  strings.
    ++  All of these functions are separated in subdirectories
    ++  by utility type.
    ++  In this section, we provide a broad overview of all of them.
      
     -ctype/ - Character classification and conversion functions
     +memory/ - memory operations
 3:  c3612a7db1b8 =  3:  8cdf0ce71aae lib/string/README: Remove strndup_a()
 4:  6757c8c928a5 =  4:  0943230b4d4f lib/string/README: Rename MEMCPY() => memcpy_a()
 5:  1249699267a0 =  5:  cb653ae17c53 lib/string/README: Document strncmp(3) and strncat(3) as being from <memory.h>
 6:  51efa2ddff9d =  6:  2312c3889cf0 lib/, src/: Move memzero() to under lib/memory/
 7:  d421d1236e18 =  7:  0ded15960a1c lib/, src/: Move strzero() to under lib/string/strzero/
 8:  99bf4380d941 =  8:  886f51695d59 lib/: Move memdup() and strndup() under lib/memory/
 9:  77990d3a2ab2 =  9:  5c627cb5a4c1 lib/, src/: Move strneq() to under lib/memory/
10:  8db526f99e40 = 10:  459e7d946156 lib/: Move strncpy/cat() to under lib/memory/

v1c

• Rebase

$ git rd
 1:  f65d2fe1b947 =  1:  8a9eff5e33f8 lib/memory/README: Add symlink to the string README
 2:  81219686b3fb !  2:  b2540e74c515 lib/string/README: Reorganize the library in memory/ and string/
    @@ lib/string/README: Don't use some libc functions without Really Good Reasons:
     +    strncpytail()
     +  Like strncpy(), but when truncating, the tail of the string is
     +  kept instead of the beginning.  This is useful for ut_id.
    -+    STRNCPYTAIL()
    ++    strncpytail_a()
     +  Like strncpytail, but takes an array.
     +
     +    strncat_a()  // To be removed
    @@ lib/string/README: strcmp/ - String comparison
     -    strncpytail()
     -  Like strncpy(), but when truncating, the tail of the string is
     -  kept instead of the beginning.  This is useful for ut_id.
    --    STRNCPYTAIL()
    +-    strncpytail_a()
     -  Like strncpytail, but takes an array.
     -
     -    strncat_a()  // To be removed
 3:  8cdf0ce71aae =  3:  8606ae5ef083 lib/string/README: Remove strndup_a()
 4:  0943230b4d4f =  4:  be3363dfd009 lib/string/README: Rename MEMCPY() => memcpy_a()
 5:  cb653ae17c53 =  5:  23c4eb8b7dc0 lib/string/README: Document strncmp(3) and strncat(3) as being from <memory.h>
 6:  2312c3889cf0 !  6:  c6a51f909e3a lib/, src/: Move memzero() to under lib/memory/
    @@ Commit message
     
      ## lib/Makefile.am ##
     @@ lib/Makefile.am: libshadow_la_SOURCES = \
    -   lockpw.c \
    -   loginprompt.c \
        mail.c \
    +   memory/memcpy/strncpytail.c \
    +   memory/memcpy/strncpytail.h \
     +  memory/memset/memzero.c \
     +  memory/memset/memzero.h \
        motd.c \
 7:  0ded15960a1c =  7:  9ca51df949ea lib/, src/: Move strzero() to under lib/string/strzero/
 8:  886f51695d59 !  8:  34e4a93bf36c lib/: Move memdup() and strndup() under lib/memory/
    @@ Commit message
     
      ## lib/Makefile.am ##
     @@ lib/Makefile.am: libshadow_la_SOURCES = \
    -   lockpw.c \
    -   loginprompt.c \
        mail.c \
    +   memory/memcpy/strncpytail.c \
    +   memory/memcpy/strncpytail.h \
     +  memory/memdup/memdup.c \
     +  memory/memdup/memdup.h \
     +  memory/memdup/strndup.c \
    @@ lib/string/strdup/strndup.c (deleted)
     
      ## lib/utmp.c ##
     @@
    - #include "alloc/malloc.h"
      #include "attr.h"
      #include "io/syslog.h"
    + #include "memory/memcpy/strncpytail.h"
     +#include "memory/memdup/memdup.h"
     +#include "memory/memdup/strndup.h"
      #include "sizeof.h"
 9:  5c627cb5a4c1 !  9:  75ced5207be8 lib/, src/: Move strneq() to under lib/memory/
    @@ lib/user_busy.c
     
      ## lib/utmp.c ##
     @@
    - #include "io/syslog.h"
    + #include "memory/memcpy/strncpytail.h"
      #include "memory/memdup/memdup.h"
      #include "memory/memdup/strndup.h"
     +#include "memory/strncmp/strneq.h"
10:  459e7d946156 ! 10:  0f1bf7265307 lib/: Move strncpy/cat() to under lib/memory/
    @@ lib/Makefile.am: libshadow_la_SOURCES = \
     +  memory/memcpy/strncat.h \
     +  memory/memcpy/strncpy.c \
     +  memory/memcpy/strncpy.h \
    +   memory/memcpy/strncpytail.c \
    +   memory/memcpy/strncpytail.h \
        memory/memdup/memdup.c \
    -   memory/memdup/memdup.h \
    -   memory/memdup/strndup.c \
     @@ lib/Makefile.am: libshadow_la_SOURCES = \
        string/strcmp/strprefix.h \
        string/strcpy/stpecpy.c \
    @@ lib/utmp.c
      #include "attr.h"
      #include "io/syslog.h"
     +#include "memory/memcpy/strncpy.h"
    + #include "memory/memcpy/strncpytail.h"
      #include "memory/memdup/memdup.h"
      #include "memory/memdup/strndup.h"
    - #include "memory/strncmp/strneq.h"
     @@
      #include "string/strchr/strnul.h"
      #include "string/strcmp/streq.h"

[ikerexxe]

One minor comment inline, apart from that this looks good

I'd also like to hear @hallyn's opinion before merging

[alejandro-colomar]

• Having merged Add strncpytail_a(), and use it instead of its pattern #1304, which already adds lib/memory/ I guess we should merge this too, for having consistently our non-string APIs out of lib/string/ in lib/memory/.

Cc: @ikerexxe , @hallyn